Forces and elasticity (5.3) (M)

Question 1

3 needed

What are the three ways you can change the shape of an object?

Answer 1

• Stretching (e.g. pulling the ends of a rubber band in opposite directions)
• Bending (e.g. archer pulls back an arrow against a bow)
• Compressing (e.g. when an empty drinks can is squashed

Question 2

Why when changing the shape of a stationary object, more than one force has to be applied?

Answer 2

The forces must act in both directions, otherwise the object will just move (be displaced)

Question 3

What is elastic deformation?

Answer 3

The change of shape is reversed when the force is removed

Question 4

What is inelastic (plastic) deformation?

Answer 4

There is a permanent change in shape - even when the forces are removed

Question 5

Describe the relationship between the extension of an elastic object, such as a spring, and the force applied to it

Answer 5

Extension (of an elastic object) and the force applied to it are directly proportional, provided that the limit of proportionality is not exceeded

Question 6

Describe the relationship between the compression of an elastic object and the force applied to it

Answer 6

Directly proportional, provided the upper limit of proportionality is not exceeded

same as with extension, but e = compression

Question 7

Describe how work is done on a spring? How is energy stored?

Answer 7

A force that stretches (or compresses) a spring does work and elastic potential energy is stored in the spring

Question 8

Describe the relationship between work done on a spring and elastic potential energy

Answer 8

Provided the spring is not inelastically deformed, the work done on the spring and the elastic potential energy stored are equal

Question 9

Describe the difference between a linear and non-linear relationship between force and extension

Answer 9

In a linear relationship, as force applied increases, extension increases at the same rate (by the same amount each time)

In a non-linear relationship, this is not true

Question 10

How do you calculate the spring constant from a linear force-extension graph?

Answer 10

Calculate gradient

Question 11

2 marks - 3 you could give

A jumper has bungee jumped and the bungee cord has been stretched. The jumper’s spine stretches a small but safe amount. Explain why?

Answer 11

There are two forces acting on the jumper

Tension (in the bungee) is pulling the jumper upwards

The jumper’s weight is pulling downwards

Question 12

2 words

When two springs are stretched by the same force, the force applied to each of them is (…)

Answer 12

shared equally