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Level 2 Physics

Relevant past NCEA Exam questions for 91171

Mechanics:

NZQA Exams, compiled by J Harris

jharris.school@gmail.com

Relationships (taken directly from the Achievement standard 91171:

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Achievement Standard

Subject Reference Physics 2.4

Title Demonstrate understanding of mechanics

Level 2 Credits 6 Assessment External

Subfield Science

Domain Physics

Status Registered Status date 17 November 2011

Planned review date 31 December 2014 Date version published 17 November 2011

This achievement standard involves demonstrating understanding of mechanics.

Achievement Criteria

Achievement Achievement with Merit Achievement with Excellence

Demonstrate understanding of mechanics.

Demonstrate in-depth understanding of mechanics.

Demonstrate comprehensive understanding of mechanics.

Explanatory Notes

This achievement standard is derived from The New Zealand Curriculum, Learning Media,

Ministry of Education, 2007, Level 7; and is..

1 Assessment is limited to a selection from the following: Motion:

constant acceleration in a straight line

free fall under gravity

projectile motion

circular motion (constant speed with one force only providing centripetal force). Force:

force components

vector addition of forces

unbalanced force and acceleration

equilibrium (balanced forces and torques)

centripetal force

force and extension of a spring. Momentum and Energy:

momentum

change in momentum in one dimension and impulse

impulse and force

conservation of momentum in one dimension

work

power and conservation of energy

elastic potential energy.

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QUESTION ONE: MOTION (NCEA SAMPLE PAPER 2012)

(a) Jason drops a stone vertically down from the top of a bridge into the water below. It

takes 2.5 s for the stone to reach the water.

Calculate the velocity of the stone when it hits the water. Use g = 9.8 m s2

. [A4]

(b) Explain the forces acting on the stone as it falls towards the water below. [M6]

(c) Explain in detail how the forces that act on the stone change as it enters the water and

sinks down to the bottom of the river bed. In your answer, you should include an

explanation of how this would affect the motion of the stone. [E8]

(d) On another occasion, Jason throws the stone from the ground at an angle of 34 to the

horizontal with a velocity of

25 m s1

as shown in the

diagram.

Determine the range by

calculating:

the velocity vector

components

the time taken to

reach maximum

height. [E8]

QUESTION TWO: FORCES (NCEA SAMPLE PAPER 2012)

Jasons dad Mike drives his car at a constant

speed around a horizontal circular track as

shown in the diagram below.

(a) The radius of the circular track is 28.0 m.

Mike drives at a constant speed. It takes

12.0 s to go around the circular track

once.

Calculate the speed and hence the

acceleration of the car.

NCEA 2012 Sample paper

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(b) Explain why the motion of the car

would be affected if there was an oil

patch on the circular path as shown in

the diagram below. (Assume that the

oil causes complete loss of friction

between the car wheels and the surface

of the track.)

In your answer, you should include:

an explanation of the forces acting on the car while it is moving in a circle

an explanation of the how the motion of the car is affected once it encounters the oil patch. [E8]

(c) On another occasion, Mike drives his car over a uniform bridge. The bridge has two

supports. The mass of the bridge is 5000 kg and the mass of Mike and his car is 1500

kg. The bridge is 30.0 m long. See the diagram below.

Calculate the support provided by end A and end B of the bridge when Mike and his car

are at a distance of 10.0 m from end A of the bridge. In your answer, you should

include arrows to show:

the weight of the bridge and the weight of the car

the support forces provided at the ends of the bridge. [E8]

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QUESTION THREE: MOMENTUM AND ENERGY (NCEA Sample paper 2012)

(a) Mikes car collides with a stationary trolley as shown in the diagram below. After the

collision, the car and trolley lock together and move as one. Calculate the final velocity

of the car and trolley together. [M6]

Mass of Mikes car = 1500 kg

Mass of trolley = 650 kg

Initial velocity of Mikes car = 18 m s1

(b) Mikes car has a long crumple zone.

Explain in detail why having this crumple zone would make a difference during impact.

In your answer, you should include ideas of velocity before and after the impact. [E8]

(c) Mikes car is towed away by a tow truck. The rope attached to the car makes an angle

of 42 with the horizontal. The rope pulls the car with a force of 850 N. The car moves

a distance of 45 m along the horizontal road during a time of 15 s. See diagram below.

Calculate:

a. the work done by the tow truck on the car.

b. the power produced by the tow truck while it is moving the car. [E8]

(d) Suspension is the term given collectively to the springs, shock absorbers, and linkages

in a car. The suspension springs on Mikes car are soft springs when compared to the

suspension springs of a truck.

Explain in detail why, in terms of spring constant and extension, a truck needs to have

stiffer suspension springs. [E8]

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KNOW THE EQUATIONS (Motion, kinematics & projectiles):

Symbols complete name And SI unit

Situation where equation is most commonly used (or notes about this equation). Use your own paper

t

dv

v

d

t

t

va

a

v

atvv if

22

1 attvd i

tvv

dfi

2

advv if 222

vf

vi

a

t

d

QUESTION FOUR: THE HIGH JUMP (NCEA 2010, Q3)

Lucy is competing in a high jump event. She runs up to the bar, jumps over it and lands on

the mat.

(a) She starts her run-up by accelerating from rest at 2.21 m s2 for 2.0 s. Calculate the distance she travels in this time. Write your answer to the correct number of

significant figures. Explain why you have used this number of significant figures.[A]

QUESTION FIVE: TRAVELLING BY CAR (NCEA 2005 Q1)

(a) A car starts from rest at traffic lights and accelerates in a straight line to a speed of 50.0 km h

1 in 10 seconds. Using

the approximation that 50.0 km h1

= 13.9 m s1

, show that the

cars acceleration is 1.4 m s2. [A]

(b) The mass of the car and its occupants is 1357 kg. Calculate the net force acting on the car when it is accelerating. [A]

Section 1 Motion:

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(c) State whether the force that you calculated in your answer to (b) is equal to, less than or greater than the total driving force provided by the cars engine. [A]

(d) Explain clearly the reason for your answer to part (c). [M]

(e) Calculate the cars power output during the first 10 seconds of its motion. Give the

correct unit for your answer. [E]

QUESTION SIX: THE BIKE RIDE (NCEA 2011 Q1)

(a) Jacquie is a bike rider. One morning she starts riding from rest and accelerates at 1.2 m s

2 for 14 seconds. Show that her final velocity

after 14 seconds is 16.8 ms-1

. [A]

(b) Jacquie then rides along a horizontal circular path at constant speed. Describe what it is that provides the force needed to keep the bike going in a circle. State

the direction of this force. [M]

QUESTION SEVEN: THE AIRCRAFT (NCEA 2007 Q1)

An aircraft is flying at a height of 600 m above the ground.

(a) Explain why the aircraft flying is not an example of

projectile motion. [M]

(b) While the aircraft is flying horizontally at a speed of 35 m s1, a packet is dropped

from it. Calculate the speed of the packet when it reaches the ground (include a vector

diagram). [E]

(e) While landing, the speed of the aircraft reduces from 80.0 m s1 to 25.0 m s1 in 8.0

seconds. Calculate the size and direction of the acceleration. Express your answer to

the correct number of significant figures. [M]

QUESTION EIGHT: The basketball throw (NCEA 2009, Q2)

Jordan then throws the basketball horizontally, with an initial horizontal velocity of 7.8 m s

1, at a

height of 1.4 m from the floor.

(a) Calculate the velocity (magnitude and

direction) of the ball just before it hits the

floor. [E]

1.4m

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QUESTION NINE: ROWING (NCEA 2006 Q1)

Steve is in a rowing race. The total mass of Steve and his

boat is 120 kg

(a) At the beginning of the race, he is at rest. When the

race starts, he accelerates to a speed of 4.5 m s1 in 5.00 s. Calculate his acceleration.

Write your answer to the correct number of significant figures. [A]

(b) Calculate the distance Steve travels in the first 5.00 s. [A]

(c) Calculate the minimum average power Steve must produce to cause this acceleration.

Write your answer with the correct unit. [E]

(d) Explain clearly why the average power Steve must actually produce will be greater

than that which you calculated in (c). [E]

(e) Later in the race, the boat is moving at constant velocity. Determine the size of the net

(or total) force acting on the boat. [A]

QUESTION TEN: THROWING THE DISCUS (NCEA 2010, Q1)

James is preparing to throw a discus by swinging it in a horizontal

circle. The diagram to the right shows the path of the discus moving

clockwise as seen from above.

(a) Draw two labelled arrows on the diagram above to show the

velocity and acceleration of the discus at the instant shown. [A]

(b) James releases the discus at the position shown in the diagram

below. Draw an arrow showing the direction the discus travels.

Explain why the discus then travels in the direction you have

drawn. [E]

(c) Before throwing the discus, James swings it round in a horizontal

circle at a constant speed of 11 m s1

. The mass of the discus is 2.1

kg, and at one time he applies a horizontal force of 290 N to it.

Calculate the radius of the discuss circular path. [M]

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James releases the discus at an angle of 37 to the horizontal.

(d) Describe the energy changes as it rises, falls, lands and rolls, coming to a stop.

You may ignore any forces caused by the air. [E]

(e) State the size and direction of the acceleration of the discus at the highest point of

its trajectory. [A]

(f) It takes 2.4 s to return to the height at which it was released, as shown in the diagram below. (James releases the discus at an angle of 37 to the horizontal.) Calculate the

speed at which he releases the discus. [E]

(g) In fact there is a vertical force acting upward on the discus called lift. Explain how this lift force would affect the horizontal distance travelled by the discus. [E]

QUESTION ELEVEN: PROJECTILE MOTION (NCEA 2006 Q3)

Marama is a long-jumper. She runs down a track, and jumps as far as

she can horizontally. Her take-off velocity is shown in the diagram

below. You can assume there is no air resistance. Acceleration due

to gravity = 9.8 ms2.

(a) Show that the horizontal component of her initial velocity is 6.0 m s1. [A]

(b) Show that the vertical component of her initial velocity is 2.2 m s1. [A]

(c) Calculate the distance she jumps horizontally. [E]

(d) State the size and direction of her acceleration at the highest point. [A]

(e) Explain why the horizontal component of her velocity is constant. [M]

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QUESTION TWELVE: TRAVELLING IN A HOT AIR BALLOON (NCEA 2005, Q3)

A hot air balloon is hovering in a stationary position, 320 m above the

sea. One of the passengers throws a tennis ball with a speed of 25 m s1

in a horizontal direction as shown in the diagram below.

(a) Assuming that it was a calm day with no wind, calculate the

horizontal distance d from the balloon to where the ball lands in

the sea. [M]

QUESTION THIRTEEN: THE SOCCER KICK (NCEA 2011, Q3)

(a) Ernies son Jacob kicks a ball towards Ernie in the garden. Ernie is 1.75 m tall. Jacob

kicks the ball with a velocity of 24 m s1

at an angle of 36 to the ground. Jacob is

standing 35 m away from Ernie.

Will the ball hit Ernie or go over his head? In your calculations, start by showing that

the horizontal component of the initial velocity of the ball is 19.4 m s1

. [E]

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KNOW THE EQUATIONS (Forces, Springs & Circles):

Symbols complete name And SI unit

Situation where equation is most commonly used (or notes about this equation).

Use your own paper

kxF -=

F 1

k

x

mgF m 2

g

22

1 kxEp EP 3

hmgEp = Ep 4

h

r

mvFc

2

FC 5

m

v

r

r

vac

2

ac 6

v

r

T

rv

2

T 7

v

r

Tf

1

f 8

T

Fd

9

F

d

Section 2 Force:

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QUESTION FOURTEEN: TRAVELLING IN A HOT AIR BALLOON

(NCEA 2005, Q3) A hot air balloon is rising vertically at a constant speed of 2.5 m s

1.

(a) Compare the sizes of the total upward force acting on the hot air balloon

with the total downward force acting on it, giving your reasons. [M]

QUESTION FIFTEEN: ERNIES MOWER (NCEA 2011, Q3)

(a) Ernie is pushing a lawn mower with a force of 26 N at an angle of 34 to

the ground, as shown below. Explain fully why not all of the 26 N force

exerted by Ernie is used to push the lawn mower horizontally along the

ground. [M]

(b) Calculate the power produced by Ernie when he accelerates the mower through a

distance of 4.0 m in 3.0 seconds. Give the correct units for your answer.[M]

QUESTION SIXTEEN: AT THE AIRPORT (NCEA 2007 Q2)

Some painters are working at the airport. They have a uniform plank resting on two supports.

The plank is 4.0 m long. It has a mass of 22 kg. The two legs that support the plank are 0.50

m from either end, as shown in the figure below.

(a) The plank is in equilibrium. Draw labeled arrows of appropriate sizes in the correct

34

26N

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position showing the forces acting on the plank on the diagram above. [M]

(b) Calculate the support force on the plank at A if a painter of mass 60 kg sits 0.75 m from A, and another painter of mass 75 kg sits at a distance of 0.80 m from B. Use g =

10 m s2. [E]

QUESTION SEVENTEEN: ROWING (NCEA 2006 Q1)

The diagram below shows part of the side of the boat and one of Steves oars as seen from above. The oar pivots on the side of the boat. The oar is 4.0 m long. Steves hand is 0.50 m from the pivot. During a warm-up, Steve exerts a force of 450 N on the oar as shown in the

diagram below.

(a) Calculate the size of the force that the oar exerts on the water. [M]

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QUESTION EIGHTEEN: THE BRIDGE (NCEA 2011, Q2)

Jacquie cycles along a uniform bridge that is supported at both ends, as shown in the

diagram.

(a) The length of the bridge is 25.0 m. The mass of Jacquie and her bike is 72 kg. The mass

of the bridge is 760 kg.

Calculate the support force (FA) provided by end A and the support force (FB)

provided by end B of the bridge when Jacquie is 5.0 m from end A. [E]

(b) Express your answers to part (a) to the correct number of significant figures. Give a

reason for your choice of significant figures in your answers to part (a). [M]

QUESTION NINETEEN: THE CAFETERIA TRAY (NCEA 2009 Q3)

Harry carries his tray of food to his cafeteria table for lunch. The uniform tray is

0.500 m long and has a mass of 0.20 kg. It holds a 0.40

kg plate of food where the centre of the plate is 0.200 m

from the right hand edge. Harry holds the tray on the left-

hand side with one hand, using his thumb as the pivot

(fulcrum), and pushes up 0.100 m from the pivot (fulcrum)

with his fingertips.

(a) State the conditions necessary for the tray to be in equilibrium. [M] (b) Calculate the weight (force of gravity) on: [A]

(i) The plate of food (ii) The tray

(c) Calculate the size of the upward force that Harrys fingertips must exert to keep the tray level. [M]

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QUESTION TWENTY: CIRCULAR MOTION (NCEA 2006 Q2)

Jan is competing in a

hammer-throw event. This

event involves swinging a

10 kg iron ball attached to a

steel wire in a horizontal

circle.

The diagrams below show

Jan and the hammer from

above.

(a) On Diagram 1, draw an arrow showing the direction of the iron

balls acceleration. Label it a. [A]

(b) On Diagram 2, draw an arrow showing the direction of the force

the steel wire exerts on Jan. Label it F. [A]

(c) Explain why a horizontal force is needed on the ball, even

though it is moving at constant speed. [E]

The ball rotates in a horizontal circle of radius 2.0 m. The time for

one rotation is 1.5 s. The iron balls mass is 10 kg. The circumference of a circle is: C = 2r.

(d) Calculate the size of the centripetal force acting on the iron ball. [E]

(e) After a few rotations, the ball has the same radius of rotation, but a shorter period. Explain what effect this will have on the horizontal force acting on Jan. [E]

QUESTION TWENTY ONE: THE BAGGAGE SECTION (NCEA 2007, Q3)

The baggage at the airport is delivered on a horizontal

circular conveyor belt that is moving at constant speed. The

radius of the circular belt is 7.0 m.

(a) Draw an arrow in the diagram below to show the direction of the velocity of the suitcase that is on

the moving circular belt. [A]

(b) Explain why the motion of the suitcase on the belt that is moving in a circle at constant speed is

accelerated motion. [E]

Diagram 1 Diagram 2

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(c) Calculate the time it takes for the belt to complete one rotation if the unbalanced force on the suitcase is 5.5 N. The mass of the suitcase is 18 kg. [E]

(d) The suitcase is on wheels. The owner pulls it across the floor

with a strap as shown in the

diagram below. The force

applied to pull the suitcase is 25

N and the strap is at an angle of

Calculate the work done

pulling the suitcase 0.80 m

along the floor. [M]

The suitcase is put on trolley A. The total

mass of trolley A and the suitcase is 33 kg.

Trolley A with the suitcase is moving with

a speed of 3.6 m s1 when it collides

inelastically with trolley B moving in the

same direction with a speed of 2.0 m s1.

The total mass of trolley B and its suitcase

is 35 kg. After the collision, trolley A is

moving with a speed of 2.4 m s1 in the

same direction.

(e) Calculate the kinetic energy of trolley B and its suitcase after the collision. [E]

(f) What assumptions did you make in order to answer the above question? [M]

(g) This collision is described as inelastic. Explain clearly what happens to momentum and kinetic energy in both elastic and inelastic collisions. [E]

QUESTION TWENTY TWO: RUA IN THE TROLLEY (NCEA 2008 Q2)

Rua then climbs onto a trolley and Tahi tows him with a rope, as shown in the diagram

below. Ruas mass is 65 kg, the mass of the trolley is 11 kg. The tension force in the rope

attached to the trolley is 95 N, and the rope is at an angle of 45 to the ground. There is a 35

N friction force on the trolley.

(a) Calculate the size of the trolleys acceleration. [E]

(b) The rope stretches 1.0 cm with the 95 N tension

force. Calculate the elastic potential energy stored

in the stretched rope. [E]

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QUESTION TWENTY THREE: MOTH IN THE WEB (NCEA 2011 Q3)

A spider spins a web in the garden and a moth gets caught in the web. The web stretches

downwards by 0.065 m when the moth of mass 0.003 kg is caught in it.

A graph for force against extension for the spiders web is shown below.

(a) Explain why the formula W = Fd cannot be used to calculate the elastic potential

energy stored in the web when the moth gets caught in it.

Your explanation should include a statement of what should be used to calculate this

energy. [E]

(b) Calculate the elastic potential energy stored in the web when the moth is caught in the

web. [M]

QUESTION TWENTY FOUR: THE POLE SWING

(NCEA 2008 Q2)

Rua goes across to the pole swing. The swing hangs on a

rope attached to a uniform beam, as shown in the diagram.

The beam is 3.0 m long and has a mass of 35 kg. The angle

between the steel wire and the beam is 37. The tension

force in the steel wire is 1500 N.

(a) The force exerted on the beam by the steel wire

can be split into two components. Show that the

vertical component of the force exerted on the

beam by the steel wire is 900 N. [A]

(b) By calculating the torques on the beam about the pivot, calculate the tension force in the rope. [M]

Force (N)

Extension (m)

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KNOW THE EQUATIONS (Energy, Momentum & Torque):

Symbols complete name And SI unit

Situation where equation is most commonly used (or notes about this equation).

Use your own paper

22

1 mvEk EK 1

m

v

hmgEp = EP 2

g

h

22

1 kxEp EP 3

k

x

FdW W 4

F

d

t

WP

P 5

t

mvp

6

m

v

tFp =

7

F

t

Section 3 Momentum and Energy:

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QUESTION TWENTY FIVE: BALL DROP: (NCEA 2009, Q1 & Q2)

(a) Jordan drops a ball onto the floor. The ball bounces up and down a few

times. Explain using energy considerations, why the height of bounce of

the ball, changes with time. [E]

(b) Jordan then picks up the throws a basketball vertically upward. Describe

and explain what happens to the velocity and acceleration of the ball

while it is in the air. [E]

QUESTION TWENTY SIX: MOMENTUM (NCEA 2006 Q4)

Marama is driving her car home after her event, when she collides with a stationary van.

Assume there are no outside horizontal forces acting during the collision.

(a) Name the physical quantity that is conserved in this collision. [A]

The mass of the car is 950 kg and the mass of the van 1700 kg.

The car is travelling at 8.0 m s1 before the collision and 2.0 m s1 immediately after the

collision, as shown in the diagram above.

(b) Calculate the size and direction of the cars momentum change. [E]

(c) Calculate the speed of the van immediately after the collision. [M]

(d) If the average force that the van exerts on the car is 3800 N, calculate how long the

collision lasts. [A]

(e) Marama had a bag resting on the front seat. Use relevant physics concepts to explain

why the bag fell onto the floor during the collision. [E]

(f) The front of modern cars is designed to crumple or gradually compress during a

collision. Use the idea of impulse to explain why this is an advantage for the people in

the car. [E]

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QUESTION TWENTY SEVEN: A COLLISION (NCEA 2005 Q2)

A car and its driver have a combined mass of 1200 kg. The car

collided with a stationary van of mass 1500 kg. The car and van

locked together after impact and from the marks on the road the

police were able to deduce that the wreckage moved at 4.0 m s1

immediately after the collision.

(a) Calculate the speed of the car just before it collided with the

van. [M]

(b) State what physical quantity is conserved in the collision. [A]

(c) State the condition necessary for the quantity you have named in (b) to be conserved.

[A]

(d) The impact lasted for 0.50 seconds. Calculate the average force that the car exerted on

the van during the collision. [E]

(e) Explain TWO features that a car has in order to reduce injury to the driver during a

collision. [E]

(f) Use calculations to explain whether the collision was elastic or inelastic. [E]

QUESTION TWENTY EIGHT: THE HIGH JUMP (NCEA 2010 Q3):

Lucy is competing in a high jump event. She runs up to the bar, jumps over

it and lands on the mat.

(a) Use physics principles to explain why it is better for Lucy to land on

the padded mat than it is to land on grass. [E]

QUESTION TWENTY NINE: JACQUIE & THE SOCCER BALL (NCEA 2011 Q2)

(a) While Jacquie is cycling at a speed of 16.8 m s1, she collides with a soccer ball that is

rolling towards her at a speed of 8.0 m s1

. The soccer ball bounces off in the opposite

direction with a speed of 5.0 m s1. Calculate Jacquies velocity (size and direction)

after the collision.

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You may ignore any effects of friction. Mass of Jacquie and her bike = 72.0 kg Mass

of soccer ball = 0.430 kg. [E]

(b) Explain what is meant by an elastic collision and an inelastic [E]

(c) Describe what you would need to do in order to determine whether this collision

between the bike and the soccer ball is elastic or inelastic. You are not required to

carry out any calculations. [E]

(d) Explain how the force exerted by the ball on Jacquie and her bike is dependent on the

duration of the time on impact, AND explain how the force exerted by the ball on

Jacquie and her bike is related to the force exerted by Jacquie and her bike on the ball.

[E]

QUESTION THIRTY: THE SHOT PUT (NCEA 2010 Q4)

Hamish is competing in the shot put. This involves throwing a 5.4

kg iron ball (the shot) as far as possible.

(a) The shot starts from rest and accelerates for 0.25 s.

Calculate the average force that Hamish exerts on the shot

if it leaves his hand at 11 m s1

. [M]

When the shot lands, it rolls along the ground at 1.5 m s1

and

collides head-on with a stationary shot which has a mass of 4.0

kg. The friction force is negligible during the collision.

After the collision, the 4.0 kg shot rolls forward at 2.4 m s1

in the same direction that the 5.4 kg shot was initially rolling.

(b) Without doing any calculations, what can you say about the total momentum

and the momentum of the 4.0 kg shot during the collision? Discuss your

answer. [E]

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(c) Calculate the velocity (size and direction) of the 5.4 kg shot after the collision. [E]

QUESTION THIRTY ONE: HARRY IN THE CREASE (NCEA 2009, Q3)

In a game of cricket, the ball approaches the batsman with a speed of 21 m s1

.

The ball has a mass of 0.161 kg. The batsman hits the ball hard with an average

force of 2560 N, and the ball moves away in the opposite direction at 30.0 m s1

.

(a) Calculate the time the ball was in contact with the bat. [M]

(b) Express your answer to (b) to the correct number of significant figures.

State the reason for your choice of significant figures

for your final answer. [M]

(c) Harry is a fielder near the batsman. Explain, using

physics principles, why Harry usually pulls back his

hand while catching a ball. [E]

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QUESTION THIRTY TWO: THE SPECTATORS (NCEA 2010, Q5)

Aroha has a mass of 55 kg. She steps onto a bench to get a better view. The bench is 4.0 m

long. When she gets on to the centre of the bench, it bends downwards 3.00 mm.

(a) Calculate the spring constant of the bench. Write your answer with the correct SI unit.

[M, A]

(b) Calculate the elastic potential energy stored in the bench [A]

Aroha then walks towards one end so that she is 1.0 m away from support B.

(c) The bench is in equilibrium. Explain what this means. [M]

(d) Support B exerts a force of 420 N on the bench. Assuming the bench is uniform;

calculate the mass of the bench. [E]

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QUESTION THIRTY THREE: THE DUTY-FREE SHOP (NCEA 2007, Q4):

At a duty-free shop at the airport, a toy teddy bear is hanging at the end of a

spring. The spring is 51.0 cm long when hanging vertically. When the teddy bear

of mass 400 g is hung from the end of the spring, the length of spring becomes

72.0 cm.

(a) Calculate the spring constant. Write a unit with your answer. [M,A]

(b) Calculate the energy stored in the spring when a second toy of mass 300 g

is also hung along with the teddy bear on the spring. [M]

(c) The 400 g teddy bear is now hung on a stiffer spring, which has double the

spring constant.

Discuss how this affects the extension and the elastic energy stored in the

spring. [E]

QUESTION THIRTY FOUR: THE HARD CHAIR (NCEA 2009,

Q3):

The springs (A) used in Harrys car seats are different from the spring

(B) that Jill uses to hang a toy spider from the ceiling of her room. The

diagram shows two types of spring.

(a) Compressing spring A by 0.20 m requires 150 J of work.

Stretching spring B by 0.30 m requires 210 J of work. By using appropriate working

and reasoning, show by calculation which spring is stiffer. [E]

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Level 2 Physics Maniacal Mechanics Matching Madness (plus common other things)

1. accelerate a) involved by reading a scale from an angle 2. acceleration due to gravity

b) alternative name for pivot

3. accurate c) stored in gravitational field when object is moved away relative to Earth

4. average velocity

d) quality that involves magnitude only

5. centripetal acceleration

e) inwards acceleration as object moves in circular path

6. centripetal force f) alternative name for standard form

7. collisions g) the rate of change of dependent variable to independent variable in a graph

8. components h) quality used to describe how steep a straight line is

9. conserved i) force needed to keep object moving in circular path

10. continuous variable

j) alternative name for torque

11. couple k) the rate of change of velocity 12. deceleration l) quantity that requires a direction

13. displacement m) length between two positions 14. distance n) alternative term for scientific notation

15. elastic potential energy

o) time taken for one revolution or event. 16. force p) rate at which objects change with velocity when dropped on Earth

17. frequency q) makes the measurement consistently larger (or smaller) than the true value

18. friction r) another term for resultant

19. fulcrum s) total displacement divided by total time 20. fundamental units

t) rate of change of displacement

21. gradient u) makes the measurement equally likely to be more or less than the true value

22. gravitational potential energy

v) any type of graph that makes a straight line with any gradient

23. hertz w) turning or twisting effect about a pivot 24. impulse x) rate of change of displacement at a particular instant

25. inelastic y) measurement close to actual value 26. instantaneous velocity

z) apparent movement of two objects due to the movement of the observer

27. joules aa) two equal and opposite forces that act at perpendicular distance apart to cause rotation

28. kinematic equations of motion

bb) rate of change of displacement of one object in relation to another

29. kinetic energy cc) negative acceleration 30. linear dd) can take any value within a range of values

31. moment ee) two vectors at right angles which, when added together, are equal to a single vector

32. momentum ff) rate of change of distance

33. net gg) number of revolutions or events in one second

34. parallax hh) change in momentum produced by a force acting for a length of time

35. parallax error ii) used only when acceleration is not changing

36. period jj) rate of change of distance of electromagnetic spectrum in vacuum

37. power kk) object following parabolic path under the force of gravity

38. precise ll) digits in a number or measurement that are not being used as place holders

39. projectile mm) when measurements are closely grouped together

40. proportional nn) rate of doing work

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41. random error oo) physical quantities that can have a range of values

42. relative velocity pp) distance traveled measured from start position to finish

43. resultant qq) when something stays constant 44. rounding error rr) seven units of the SI system from which all others can be derived

45. scalar ss) physical quantity of the mass multiplied by the rate of change of displacement

46. scientific notation

tt) equivalent single vector when two or more vectors are acting on an object

47. significant figures

uu) when the measuring scale does not give accurate value for nil measurements

48. slope vv) SI unit for the number of cycles per second

49. speed ww) process of transforming energy form one form to another

50. speed of light xx) force in connected strings and ropes that tries to stretch them

51. spring constant yy) when two or more objects interact 52. standard form zz) SI unit of energy

53. systematic error

aaa) produced when two surfaces come in contact

54. tension bbb) force required to compress or extend a spring one metre

55. torque ccc) when two qualities are related by a constant ratio

56. uncertainty ddd) SI unit of rate of change of work

57. variables eee) property of object while in motion 58. vector fff) how a measurement could differ from the true value

59. velocity ggg) where kinetic energy is not conserved in collision

60. watt hhh) stored in an extended or compressed spring

61. work iii) push or pull in a particular direction 62. zero error jjj) introduced into calculations caused by using partial previous answers