34

Index

I. Do we know?

II. Points of Content

A. Machines

i. Definition

ii. Functions and Uses

iii. Technical terms

iv. Principle

v. Relation between Efficiency, M.A. And V.R.

B. Levers

i. Definition

ii. Principle

iii. Kinds of Levers

(1) Class I Levers

(2) Class II Levers

(3) Class III Levers

(4) Levers in human body

iv. Numericals

C. Inclined plane

i. Definition

ii. Mechanical Advantage

D. Pulleys

i. Types

ii. Single fixed pulley

(1) Mechanical advantage

(2) Velocity ratio

(3) Efficiency

iii. Single movable pulley

(1) Mechanical advantage

(2) Velocity ratio

(3) Efficiency

iv. Combination of block and tackle pulleys

v. M.A.,V.R., Efficiency of combination of block and tackle pulleys

34

vi. Numericals

E. Mindmaps/diagrams/tables/charts

III.Objective Questions

1. Machines as force multipliers;

1. load, effort, mechanical advantage, velocity ratio and efficiency;

2. Simple treatment of levers, inclined plane and pulley systems showing the

utility of each type of machine.

1. Machines as force multipliers; load, effort, mechanical advantage, velocity ratio and efficiency; simple treatment of levers, inclined plane and pulley systems showing the utility of each type of machine.a. Functions and uses of simple machines.

b. Technical terms: effort E, load L, mechanical advantage , velocity

ratio , input (Wi), output (Wo),efficiency(),

c. Relation between and MA,VR ;for all practical machines <1; MA < VR.d. Inclined plane: MA, VR and . [No derivation details].

2. Lever: principle (for an ideal lever only), ;

a. 1st , 2nd and 3rd class of levers; examples: MA and VR in each case.b. Examples of each of these classes as found in the human body.

3. Pulley system; simple fixed, single movable, combination of movable pulleys, block and tackle; MA, VR and in each case.[No derivation details.]4. Utility of each type of machine. Simple numerical problems.

34

A. Machines

i. Definition

Q.1. What do you understand by a simple machine?

Ans. A machine is a device by which we can either overcome a large resistive force

at some point by applying a small force at a convenient point and in a desired

direction or by which we can obtain a gain in speed.

ii. Functions and Uses

Q.1. State four ways in which machines are useful to us.

Ans. The machines perform the following functions and they are useful to us in the

following four ways:

i) In lifting a heavy load by applying a less effort, i.e., as a force multiplier.

ii) In changing the point of application of effort to a convenient point.

iii) In changing the direction of effort to a convenient direction.

iv) For obtaining a gain in speed (i.e., a greater movement of load by a smaller

movement of effort).

Q.2. Give an illustration of the following use of a simple machine:

i) to obtain gain in force,

ii) to change the direction of force,

iii) to obtain gain in speed.

Ans.

i) Pliers

ii) A Car jack

iii) Bicycle

iii. Technical terms

Q.1. Define effort.Ans. Effort is the external force applied to a simple machine

Q.2. Define Load.Ans. Load is the force against which the machine does the work

34

Q.3. Explain the term mechanical advantage. State its unit.

Ans. Mechanical Advantage (MA)= It has no unit

When is the mechanical

advantage of a machine 1?

when the machine

changes direction

When is the mechanical

advantage of a machine less than

1?

When the machine

increases distance

When is the mechanical

advantage of a machine greater

than 1?

when the machine

increases force

Q.3. Define the term velocity ratio. State its unit.

Ans. Velocity Ratio (VR) is defined as the ratio of displacement of effort (dE) to the

displacement of load (dL) in the same interval of time. It has no unit.

Velocity Ratio (VR)=

Q.4. Define the term efficiency of a machine.

Ans. Efficiency of the machine () is the ratio of the work done on the load to the

work done by the effort. Efficiency () =

Note: Efficiency is always expressed as percentage

Q.5. Why is a machine not 100% efficient?

Ans. No machine is ideal or 100% efficient for the following reasons :

i) the moving parts in it are not frictionless

ii) the string in it if present, is not perfectly elastic.

iii) its different parts are not perfectly rigid, and

iv) its moving parts are not weightless.

Due to above factors there is always some loss of energy in the machine. Thus,

the output energy from a machine is always less than the input energy to it .

34

iv. Principle

Q.1. What is the purpose of a machine?

Ans. The purpose of a machine is to make the work easier by either reducing effort

or changing the point of application of force or changing the direction of force or

increasing the speed.

Q.2. What do you understand by an ideal machine?

Ans. An ideal machine has an efficiency of 100%.A machine in which work inputs

equals work output; such a machine would be frictionless.

v. Relation between Efficiency, M.A. And V.R.

Q.1. State the relationship between mechanical advantage, velocity ratio and efficiency.

Ans.                     =   = 

Q.2. Derive the relationship between the terms mechanical advantage, velocity ratio and

efficiency as applied to a machine.

Ans. Consider actual machine which displaces a useful load through a distance

when effort

          'E' causes a displacement through distance 'D'.

            Output = Work done in displacing load.

                              =    .

                 Input = work done by effort in causing displacement

                          =

               Efficiency =  =   =   =  = 

                    =   = 

34

B. Levers

i. Definition

Q.1. What is a lever?

Ans. A lever is a simple machine. A lever bar exerts a force to move a load by

turning on a pivot or fulcrum.

ii. Principle

Q.2. State the principle of a lever.

Ans. For equilibrium, the moment of the effort about the fulcrum must be equal and

opposite to the moment of the weight (Load) about it. So that, we have

Effort × effort arm = Weight × weight arm.

This is known as the principle of lever.

Q.3. Write down a relation expressing the mechanical advantage of a lever.

34

Ans. By the principle of moments, in state of equilibrium, for all types of levers,

we have,

LOAD × load arm = Effort × effort arm

Or

i.e. Mechanical advantage of a lever =

Clearly, therefore, the longer the effort arm and the shorter the weight arm, the greater

is the mechanical advantage of the lever.

Q.3. What is the use of the lever if its mechanical advantage is less than 1?

Ans. Although levers have MA less than 1, they help to get gain in force, or gain in

speed, thereby help us apply force at a convenient place to enable movement of effort

over a large distance.

iii. Kinds of Levers

Q.1. Name the three classes of levers and distinguish between them. Give two examples of

each class

Ans. _______________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

Q.2. The following are examples of levers. State the class of levers to which each one

belongs giving the relative positions of Load (L), Effort (E) and Fulcrum (F):

i) Scissors

ii) Sugar tongs.

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iii) Nut cracker

iv) pliers.                                                                   

Ans.

No.Name of

LeverOrder of

Lever

Position of

Load (L) Effort (E) Fulcrum (F)

(i) Scissors First One end Other end At centre

(ii)Sugar tongs

Third One end At centre Other end

(iii)Nut

cracker Second At centre One end Other end

(iv) Pliers First One end Other end At the centre

  

Q.3. Which type of lever has a mechanical advantage always more than one? Give one

example. What change can be made in this lever to increase it mechanical advantage?

Ans. In a lever of the second Class, we always have effort arm > Load arm and

hence the mechanical advantage in this case must always be greater than

1.__________________________________________________________________________

___________________________________________________________________________

Q.4. Draw diagrams to illustrate the positions of fulcrum, load and effort, in each of the

following:

i) A seesaw

ii) A common balance

iii) A nut cracker

iv) Forceps.

34

(1) Class I Levers

Features of Class One Lever Fulcrum is in between load and effort By adjusting the position of fulcrum towards load the mechanical advantage of the class one lever can be increased Examples: pair of scissors, See – Saw, Crowbar ,Water pump, Pliers, Claw hammer

Q.1. Give two examples of class I lever.

Ans. _______________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

Q.2. Class I lever is that in which:

i) fulcrum is between the load and effort

ii) load is between the fulcrum and effort

iii) effort is between the load and fulcrum

iv) Fulcrum, load and effort are at one point.

Ans. Fulcrum is between the load and effort

34

Q.3. Give one example each of a Class I lever where mechanical advantage is (a) more

than one, and (b) less than one.

Ans. _______________________________________________________________

_____________________________________________________________________

____________________________________________________________________

Q.4. Give an example of a class I lever which has mechanical advantage equal to 1. How

can the mechanical advantage of this lever be made greater than one?

Ans. _______________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

Q.1. A pair of scissor and a pair of pliers both belong to the same class of levers. Name the

class of lever. Which one has the M.A. less than 1?

Ans. Class I, Scissors

Q.4. Explain why scissors for cutting cloth may have blades longer than the handles, but

shears for cutting metals have short blades and long handles.

Ans. Shears, used for cutting the thin metal sheets, have much longer handles as

compared to its blades. Hence, In a shear, the effort arm is longer than the load arm,

the mechanical advantage and the velocity ratio of the lever are greater than 1. Such a

lever serves as a force multiplier, i.e., it enables us to overcome a large resistive force

(load) by a small effort. However, In a scissor , effort arm is shorter than the load arm,

its mechanical advantage and velocity ratio both are less than .Such levers are used to

obtain gain in speed because the velocity ratio less than 1 implies i.e., the

displacement of load is more as compared to the displacement of effort. The scissors

is used to work on loads (cloth, paper, etc) with high speed.

Q.2. Draw a labelled diagram of a Class I lever. Give one example of such a lever.

Ans.

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(2) Class II Levers

Characteristics of Class Two Lever Load is in between effort and fulcrum Mechanical advantage is always greater than one, because effort arm is always greater than load arm.  Examples: Nut cracker, Wheelbarrow, Bottle opener, Lemon squeezer

Q.1. Give two examples of class II lever.

Ans. _______________________________________________________________

_____________________________________________________________________

____________________________________________________________________

Q.3. Explain why the M.A. of a Class II type of lever is always more than one.

Ans. _______________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

____________________________________________________________________

Q.4. Draw a labelled diagram of a Class II lever. Give one example of such a lever.

Ans.

34

(3) Class III Levers

Characteristics of Class Three Lever Effort is between fulcrum and load Mechanical advantage is always less than one because effort arm is always smaller than load arm Examples: Fire tongs, Forceps, Forearm ,Fishing rod  

 

Q.1. Give two examples of class III lever.

Ans. _______________________________________________________________

_____________________________________________________________________

____________________________________________________________________

Q.2. Explain why the M.A. of the class III type of lever is always less than one.

Ans.  By principle of Machines, Effort × Effort ARM = load × Load ARM 

In class-III levers effort E is in between the fulcrum F and Load L 

In this case, Effort ARM < Load ARM,

   <1

M. A =  

 M. A < 1 

Q.3. Class III levers have mechanical advantage less than one. Why are they then used?

34

Ans. With Class III type of levers we do not get gain in force, but we get gain in

speed i.e., a larger displacement of load is obtained by a smaller displacement of

effort. For example, the blade of a knife moves longer by a small displacement of its

handle.

Q.4. Draw a labelled sketch of a Class III lever. Give one example of this kind of lever.

Example:

Q.5. The lever for which the mechanical advantage is less than one has:

i) fulcrum at mid point between load and effort

ii) load between effort and fulcrum

iii) effort between fulcrum and load

iv) Load and effort acting at the same point.

Ans. Effort between fulcrum and load.

(4) Levers in human body

   

34

M-effort

F-Fulcrum

R-Load

Q.1. Give example of each class of lever in a human body.

Ans.

i) Class 1: In the action of nodding of the head, the spine acts as the fulcrum, load

is at its front part, while effort is at its rear part. Thus this is an example of Class I

lever.

ii) Class2: The fulcrum is at toes at one end, the load (i.e., weight of the body) is in

the middle and effort by muscles at other end. Thus this is an example of Class II

lever.

iii) Class 3: The elbow joint acts as fulcrum at one end, biceps exerts the effort in the

middle and a load on the palm is at other end. Thus this is an example of Class III

lever.

C. Inclined plane

Inclined Plane

i. Definition

Q.1. What is an inclined plane? Give two examples where it is used to raise a heavy load

with less effort.

Ans. An Inclined plane or a ramp is one of the basic machines. It reduces the force

necessary to move a load a certain distance up by providing a path for the load to

move at a low angle to the ground. This lessens the needed force but increases the

distance involved, so that the amount of work stays the same. Examples are ramps,

sloping roads, chisels, hatchets, and wedges.

34

Q.2. The force needed to push a load up an inclined plane is less than the force needed to

lift it directly. Give a reason.

Ans. _______________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

ii. Mechanical Advantage

Q.1. Write an expression for the mechanical advantage of an inclined plane in terms of its

length / and vertical height h.

Ans. _______________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

Q.2. ‘Steeper the inclined plane more is the effort needed to push a load up the plane’.

Explain it.

Ans. _______________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

D. Pulleys

34

Pulley A pulley is a flat circular disk, having a grooved rim and capable of revolving around a fixed point passing through its centre.

Q.1. The efficiency of a pulley is always less than 100%.Why?

Ans. _______________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

34

i. Types

ii. Single fixed pulley

Fixed Pulleys-Features Single fixed pulley is classified as a lever of class I The fulcrum is at the centre and the load arm and effort arm have the same length It is used to change the direction of force

Q.1. What is a fixed pulley?

34

Ans. _______________________________________________________________

_____________________________________________________________________

Q.2. Given one use of a single fixed pulley.

Ans. _______________________________________________________________

_____________________________________________________________________

Q.3. In a single fixed pulley, if the effort moves by a distance x downwards, by what

height is the load raised?

Ans. x

(1) Mechanical advantage

Q.4. What is the ideal mechanical advantage of a single fixed pulley?

Ans. _______________________________________________________________

_____________________________________________________________________

Q.5. There is no gain in mechanical advantage in the case of a single fixed pulley. Explain,

why the pulley is then used?

Ans. The single fixed pulley inverts the direction of the force. An upward force on

the load is changed to a downward pull. This is very convenient to lift load. So it is

used very often.

(2) Velocity ratio

Q.1. In a single fixed pulley, why is the velocity ratio always more than the mechanical

advantage?

Ans. _______________________________________________________________

_____________________________________________________________________

(3) Efficiency

Q.1. What is the efficiency of the single fixed pulley?

Ans. _______________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_______________________________________________________________

34

iii. Single movable pulley

Features-Single Movable Pulley system It consists of two pulleys A and B The pulley A is fixed The pulley B is movable The pulley A helps in changing the direction of effort applied Q.1. What is a single movable pulley? What is its mechanical advantage in the ideal case?

Ans. _______________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_______________________________________________________________

Q.2. Name the type of single pulley that can act as a force multiplier. Draw a labelled

diagram of the pulley mentioned by you.

Ans. Single moveable pulley

Q.3. Give two reasons why the efficiency of a single movable pulley system is not 100%.

Ans. _______________________________________________________________

_____________________________________________________________________

Q.4. In which direction the force need be applied, when a single pulley is used with a

mechanical advantage greater than one?

34

Ans. _______________________________________________________________

_____________________________________________________________________

Q.5. Show how a single pulley can be used to reduce the effort required to overcome a

given load. Draw a diagram of the system. Why is it generally more convenient to use

two pulleys for this?

Ans. _______________________________________________________________

_____________________________________________________________________

Q.6. In a single movable pulley, if the effort moves by a distance x upwards, by what

height is the load raised?

Ans.

(1) Mechanical advantage

Q.1. What is the mechanical advantage of a single moveable pulley?

Ans. _______________________________________________________________

_____________________________________________________________________

(2) Velocity ratio

Q.1. What is the velocity ratio of a single moveable pulley?

Ans. _______________________________________________________________

_____________________________________________________________________

(3) Efficiency

Q.2. What is the efficiency of a single moveable pulley?

Ans. _______________________________________________________________

_____________________________________________________________________

34

iv. Combination of block and tackle pulleys

Q.7. What is a block and tackle system of pulleys?

Ans. _______________________________________________________________

_____________________________________________________________________

Q.8. Draw a diagram of a block and tackle system of pulleys having a velocity ratio of 5.

In your diagram indicate clearly the points of application and the direction of the load and

effort. Also mark the tension in each strand.

Ans. _______________________________________________________________

_____________________________________________________________________

Q.9. In case of a block and tackle arrangement, the mechanical advantage increases with

the increase in the number of pulleys .Explain.

Ans. _______________________________________________________________

_____________________________________________________________________

Q.10. The lower block of a block and tackle pulley system must be of negligible weight.

Why?

Ans. _______________________________________________________________

_____________________________________________________________________

34

Q.11. In a block and tackle system consisting of 3 pulleys, a load of 75 kgf is raised with an

effort of 25 kgf. Find the mechanical advantage, velocity ratio and efficiency.

Ans. Ans. 3, 3, 100%

Q.12. A block and tackle system has 5 pulleys. If an effort of 1000 N is needed to raise a

load of 4500 N, calculate:

i) mechanical advantage,

ii) velocity ratio, and

iii) Efficiency of the system.

Ans.

i) 4.5

ii) 5

iii) 90%

Q.13. In the diagram, draw a tackle to lift a load by applying the force in a convenient

direction. Mark the position of load and effort.

i) If the load is raised by 1 m, through what distance will the effort move?

ii) State how many strands of tackle are supporting the load?

iii) What is the mechanical advantage of the system?

Ans.

i)

ii)

iii)

v. Numericals

TYPE 1

PROB. 1. A resistance of 1500 N is overcome by a machine of V.R 6 and efficiency

80%. Find   

i) Mechanical advantage

ii) Effort required to overcome resistance. (2mks)

Ans.

i) = ,

34

M.A.= ×V.R. = ×6=4.8

ii)

.

PROB. 2. The diagram below shows a lever in use.

i) To which class of lever does it belong?

ii) If AB = 1 m, AF = 0.4 m, find its mechanical advantage.

iii) Calculate the value of E.

Ans.

i) Class I

ii) 1.5

iii) 10

PROB. 1. The crowbar is a type of lever as shown below:

A crowbar of length 150 cm has its fulcrum at a distance of 25 cm from the load. 

Calculate the mechanical advantages of this crowbar.                  (2)

PROB. 2.  A cook uses a 'fire tong' of length 28 cm to lift a piece of burning coal of mass 250 g. 

If he applies his effort at a distance of 7 cm from the fulcrum, what is the effort in S.I. unit? Take 

g = 10 m/s2.

PROB. 3. A crowbar of length 120 cm has its fulcrum situated at a distance of 20 cm

from the load. Calculate the mechanical advantage of the crowbar.

Ans. 5

PROB. 4. A 4 m long rod of negligible weight is to be balanced about a point 125 cm

from one end. A load of 18 kgf is suspended at a point 60 cm from the support on the

shorter arm.

i) A weight W is placed 250 cm from the support on the longer arm. Find W.

ii) If W = 5 kgf, where must it be kept to balance the rod?

iii) To which class of lever does it belong?

34

Ans.

i) 4.32 kgf

ii) 2.16 m from support on longer arm

iii) Class I.

PROB. 5. A pair of scissors has its blades 15 cm long, while its handles are 7.5 cm long.

What is its mechanical advantage? Ans. 0.5

PROB. 6. A force of 5 kgf is required to cut a metal sheet. A shears used for cutting the

metal sheet has its blades 5 cm long, while its handle is 10 cm long. What effort is needed

to cut the sheet? Ans. 2.5

PROB. 7. A boy has to lift a load of mass 50 kg to a height of 1m. What effort is

required if he lifts it directly? Take g = 10 N kg -1. But he can exert a maximum effort of

250 N, so he uses an inclined plane to lift the load up. What should be the minimum

length of the plank used by him?

PROB. 8. A coolie uses a sloping wooden plank of length 2.0 m to push up a drum of

mass 100 kg into the truck at a height 1.0

i) What is the mechanical advantage of the sloping plank?

ii) How much effort is needed to push the drum up into the truck?

iii) What assumption have you made in arriving at the answer in part (ii) above?

i. Ans. (i) 2 (ii) 50

TYPE 2 PULLEYS

34

PROB. 1. The diagram alongside shows a system of 5 pulleys.

i) Copy the diagram and complete it by drawing a string around the

pulleys. Mark the position of load and effort.

ii) If the load is raised by 1 m, through what distance will the effort move?

Ans.

i) The complete diagram of a string around the pulleys is shown as

follows  with the marked positions of effort and load.

ii) Let the distance moved by the effort = D

Distance moved by the load = d = 1 m (given)

Let the load = W

and the effort applied = E 

By the principle of machines 

Therefore,

But  = 5

Hence D = ×d =  5 x  1 m                               

D = 5 m                                                                                 

34

                                                                                         

PROB. 2. DIAGRAM below gives an arrangement of single moving pulleys.

i) If the effort applied at the free end of the string is E, show the direction

and magnitude of the forces exerted by the four strings marked (1) to

(4).

ii) what is the load which can be lifted by the effort ?

iii) calculate the mechanical advantage of the system of pulleys.

Ans.

34

i)

ii) Suppose the load lifted = L

But effort applied = E    (given)

Let the effort Arm =

Then the load Arm =

Now, by the principle of machine

Load × load Arm = Effort × Effort Arm

i.e

Therefore , L  = 4E

iii) M.A is defined as the ratio of the load lifted by the machine to the effort

applied on the machine

i.e M.A  = = 4

Hence, M.A = 4

PROB. 1. The diagram below shows a pulley arrangement. In the diagram, mark the

direction of the force due to tension, acting on the pulley A

i) What is the purpose of the pulley B?

ii) If the tension is T Newton, deduce the relation between T and E.

34

iii) Calculate the Velocity ratio of the arrangement.

iv) Assuming that the efficiency of the system is 100%, what is the mechanical

advantage?

v) Calculate the value of E.

PROB. 2. A pulley system has a velocity ratio 3 and an efficiency of 80%. Draw a

labelled diagram of this pulley system. Calculate the mechanical advantage of the system

and the value of the effort required to raise a load of 300 N.

PROB. 3. In a system of four pulleys, the lower two pulleys are movable and the upper

two are fixed.

i) Draw a string around the pulleys. Also show the place and direction in which the

effort is applied.

ii) What is the velocity ratio of the system?

iii) What is the mechanical advantage of the system?

iv) What assumption do you make in arriving at your answer in part (iii)?

PROB. 4. A block and tackle system has 5 pulleys. If an effort of 1000 N is needed to

raise a load of 4500 N, calculate:

i) mechanical advantage

ii) velocity ratio, and

iii) efficiency of the system.

PROB. 5. Draw a diagram of block and tackle system of pulleys having a velocity ratio

of 5. In your diagram indicate clearly the points of application and the direction of the

tension in each strand.

34

E. Mind maps/diagrams/tables/charts

34

      

  

34

 

   Objective QuestionsQ.1. What is the relationship between the mechanical advantage and the velocity ratio for

i) an ideal machine,

ii) a practical machine.

Ans.

i) M.A. = V.R.

ii) M.A. < V.R.

Q.2. Mechanical advantage (M.A.), load (L) and effort (E) are related as:

i) M.A. = L × E

ii) M.A. × E = L

iii) = M.A.× L

iv) None of these.

Ans. M.A. × E = L

Q.3. The correct relationship between the velocity ratio (V.R.), distance moved by load

and distance moved by effort is:

Ans. The correct relationship between the mechanical advantage (M.A.), the

velocity ratio (V.R.) and the efficiency ( ) is:

i) M.A. = × V.R.

ii) V.R. = × M.A.

iii) = M.A. × V.R.

iv) None of these

Ans. M.A. = × V.R.

Q.4. For an ideal machine, the ratio of mechanical advantage (M.A.) to the velocity ratio

(V.R.) is:

i) greater than one

ii) less than one

iii) equal to one

iv) Depends on the value of load.

Ans. equal to one

Q.5. Which of the following statements is not true for a machine:

i) It always has efficiency less than 100%.

34

ii) Mechanical advantage can be less than one.

iii) It can also be used as a speed multiplier.

iv) It can have a mechanical advantage greater than the velocity ratio.

Ans. It can have mechanical advantage greater than the velocity ratio

Q.6. To which class of levers do the following belong?

i) Wheel barrow

ii) Nut cracker

iii) Crowbar

iv) Fishing rod

v) Forearm

vi) Fire tongs

vii)Physical balance

viii) Seesaw

ix) Rowing oar of a boat

x) Forceps

xi) Opening a door

xii)Opening a box

xiii) Motor car foot-brake

xiv) Knife.

Q.7. What are the parts of a lever?

i) effort, fulcrum, load

ii) fulcrum, force, load

iii) resistance, effort, fulcrum

iv) all of the above

Q.8. Which of the following are all simple machines?

i) lever, wedge, inclined planeii) wheel and axle, screw, wedgeiii) pulley, wedge, inclined plane

34

iv) all of the above

Q.9. An axe is an example of what simple machine?

i)   inclined planeii)   pulleyiii)   wedge (correct answer)iv)   screw

Q.10. A door is an example of what simple machine?

i) inclined planeii) wedgeiii) screwiv) lever (correct answer)

Q.11. A flagpole is an example of what simple machine?

i) screwii) pulley (correct answer)iii) inclined planeiv) lever

Q.12. When using an inclined plane. The work is easier. Simple machines

only make work easier and do not do less work. How do inclined planes

make up this difference?

i) move an object over a longer distance (correct answer)ii) move an object over a shorter distanceiii) there is no difference

Q.13. When do you need less force using a lever?

i) when the fulcrum and effort are close togetherii) when the fulcrum and force are close togetheriii) when the load and fulcrum are close together (correct answer)iv) the distance does not make a difference

Q.14. The ramps at the astrodome represent what simple machine?

i) pulleyii) inclined plane (correct answer)iii) wheel and axle

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iv) lever

Q.15. What are the two (2) kinds of pulleys?

i) moveable and non-moveableii) fixed and non-moveableiii) moveable and fixed (correct answer)iv) fixed and hooked

Q.16. A ramp is an example of this type of simple machine

i) inclined plane ii) pulley iii) lever iv) wedge

Q.17. This makes raising a flag up a flagpole much easier inclined plane

i) pulley ii) lever iii) fulcrum

Q.18. A screw is actually one of these wrapped around a post One answer only. 

i)  inclined plane ii) pulley iii) lever iv) fulcrum

Q.19. Two simple machines found in a pair of scissors

i) lever, wedge, sometimes wheel and axle ii) pulley iii) lever iv) fulcrum

Q.2. For greater efficiency of a block and tackle pulley system:

i) the lower block should be of negligible

ii) the upper and lower blocks should be of equal weights

iii) the lower block should be heavier than the upper block

iv) the weight of rope should be equal to the weight of pulleys.

Ans. the lower block should be of negligible weight

Q.3. State true or false.

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i) The velocity ratio of a single movable pulley is always 2.

ii) The velocity ratio of a single fixed pulley is always more than 1.

iii) The velocity ratio of a block and tackle system is always equal to the number of

strands of the tackle supporting the load .

Ans.

i) T

ii) F

iii) T

Q.20. State whether the mechanical advantage of an inclined plane is equal to 1, less than 1

or greater than 1? Ans. Greater than 1

Ans.