TITLE: P2 Revision 11A5

Objectives• How do we measure the extension of an object

when stretched? – grade C• What is the spring constant of a spring? – grade C• What is Hooke’s law? – grade C

KEY WORDS:

StretchSquash

ExtensionEnergySpring

constant force

NewtonsMetre

ExtensionProportional

Limit of proportionalit

y

Outcomes:• Use the revision PowerPoint to complete the set

activities in preparation for your mock examination

• Complete the terminal velocity card sort with Mrs Potts

What is meant by Resultant Force?(Use to help with slide 3 and 4)

The differences between the forces acting on an object to create an overall single force.

Resultant Force = zero when an object is stationary or at a constant speed if moving

Resultant Force = not zero when an object is accelerating or decelerating

What is the resultant force for each car?

A =

B =

DESCRIBE the motion of each car and EXPLAIN why?

A =

B =

Why have speed limits?

The faster a vehicle is driving, the longer it will take to stop – the overall distance this takes is the stopping distance.

stopping distance = t_______ distance + b_____ distance

What affects thinking distance?The thinking distance is the distance a vehicle travels in the time it takes for a driver to react to a situation and apply the brakes.

What factors will affect thinking distance? – 3 images

Is a tired driver as dangerous as a drunk driver?

• http://www.bbc.co.uk/learningzone/clips/risks-of-driving-when-tired/8323.html

What affects braking distance?The braking distance is the distance a vehicle takes to stop once the driver has applied the brakes.

What factors will affect braking distance? – 3 images

Factors affecting stopping distances

What does the graph show?

What is the difference in speed of the cars?

Velocity time graphs – label the points

• A• B• C

Acceleration

Deceleration

Constant speed

A

B

C

Investigation

• What is meant by extension?

Limit of proportionality?

• What is meant by this term?

• Label with a star the limit of proportionality on the rubber band and polythene strip

Hooke’s Law

• The extension of an elastic object is directly proportional to the force applied, provided that the limit of proportionality is not exceeded:

Formula:• F = k x e– F is the force in newtons, N– k is the spring constant in newtons per

metre, N/m– e is the extension in metres, m

The spring constant

• The spring constant is the force per unit extension needed to extend the spring, assuming you do not exceed the limit of proportionality.

• The stiffer a spring is, the g_____ its spring constant.

Complete the example (grade C)

• A spring has a spring constant of 25 N/m. How much force is needed to extend the spring by 0.1m?

• F = k x e• F =

Using bbc bitesize (grade C)

• Resaerch the equations and UNITs for each one and an example calculation:

• Momentum equation• Work done equation• Weight equation

• Print out the handout as a revision tool