Forces 3 - forces and elasticity

Question 1

Examples of elastic materials

Answer 1

Spring
Rubber band
Eraser
Playground surface
Tennis ball
Rubber gloves

Question 2

Define elastic material

Answer 2

Elastic materials are materials that always return to their original shape, size and length after the stretching, bending or compressing force has been removed

Question 3

How can objects change shape

Answer 3

They can change their shape by stretching, bending and compression

Question 4

What is elastic deformation

Answer 4

Elastic deformation occurs when objects return to their original shape when the stretching, bending or compressing force is removed

Question 5

Explain two properties of the spring that makes it suitable for use in the balance.

Answer 5

deforms elastically
(so) will return to its original
length / shape (after force is
removed)

compression is directly
proportional to the force
(applied)
(so) gives a linear scale

Question 6

Materials that undergo elastic deformation/elastic materials

Answer 6

Springs

Question 7

Define inelastic deformation

Answer 7

Inelastic deformation occurs when an object remains stretched and does not completely return to their original shape even when the stretching force is removed

Question 8

In order to change an objects length or shape how many forces are needed to be applied
explain why

Answer 8

In order to change an object’s length or shape, then we have to apply more than one force

If we only applied one force to a stationary object, then the forces are no longer balanced
In this case the object would simply move (rather than changing length or shape)

Question 9

what would happen if we only applied one force to a stationary object

Answer 9

If we only applied one force to a stationary object, then the forces are no longer balanced
In this case the object would simply move (rather than changing length or shape)

Question 10

examples of inelastic materials/materials that undergo inelastic deformation

Answer 10

Plastic

Question 11

State the equation that links force, extension and spring constant

Answer 11

F = k x e

Force -Newtons
Spring constant - k - N/m
Extension - e - metres

Question 12

What happens when an elastic object is stretched or compressed
what is stored in the object?

Answer 12

When we stretch or compress an elastic object, we are using a force to do work.
In this case, elastic potential energy is stored in the object

Question 13

work done = _____
only true _________________

Answer 13

work done = elastic potential energy store
only true when the object is not inelastic deformed

Question 14

The variables of practical that investigates how the force applied to a spring affects the extension of the spring

Answer 14

Independent variable = Force applied to the spring
Dependent variable = Extension of the spring
Control variable = Spring (same spring used throughout the experiement)

Question 15

Equipment for the experiment that investigates how the force applied to a spring affects the extension of the spring

Answer 15

Bosses
Clamps
Clamp stand
Heavy weight
spring
metre ruler

Question 16

State the method for investigating how the force applied to a spring affects the extension of the spring

Answer 16

Set up the equipment using the G-clamp stand to secure the clamp stand to the desk

Place a heavy weight on the clamp stand to stop it from falling over

hang the spring from the clamp

use a second clamp and boss to fix a (half) metre rule alongside the spring
It is really important that the metre rule is vertical otherwise the reading will be inaccurate

The top of the spring must be at the zero point on the metre rule

The bottom of the spring has a wooden splint attached as a pointer. This pointer must be horizontal of the readings will be inaccurate

Now read the position of this pointer on the metre rule. This is the unstretched length of the spring

Hang a 1N weight on the spring.
Read the new position of the pointer on the metre rule.

Continue adding 1N weights to the spring and reading the position of the point

For each new force record the position of the
calculate the extension produced
To do this subtract the length of the unstretched spring from each reading

Unload the spring and repeat twice more to calculate a mean

Question 17

State some risks assessment to this hookes law practical

Answer 17

Hazard: Clamp (stand, boss and masses) might fall off desk

Risk: injury to feet

Precaution: Use clamp to fix apparatus to the bench

Put (heavy) masses on the base/foot of the stand

Stand up so that you can move out of the way

Hazard: Spring could break / come loose

Risk: damage eye

Precaution: Wear safety goggles

Question 18

Explain why it is important for the metre rule to be vertical

Answer 18

It is really important that the metre rule is vertical otherwise the reading will be inaccurate

Question 19

How do we know that the extension is directly proportional to the force

Answer 19

The graph is a straight line passing through the origin (zero)

Question 20

What type of relationship is there between force and extension

Answer 20

Extension is directly proportional to force
There is a linear (not a non-linear relationship) relationship between force and extension (this is because we get a straight line graph)

Question 21

How do we know that the graph shows that the spring is elastic

Answer 21

This graph shows that the spring is elastic
This is because if we remove the weight, the extension returns to zero

Question 22

When does the force/extension graph stop being a straight line

Why does the graph look like this
https://bam.files.bbci.co.uk/bam/live/content/zxbdng8/small

Answer 22

If we add too much weight to the spring
This shows we have reached the limit of proportionality

Question 23

https://bam.files.bbci.co.uk/bam/live/content/zxbdng8/small
What type of graph is this

Answer 23

The graph is now non-linear

Question 24

How can you know if you have overstretched a spring

Answer 24

If we took all the weight away, the spring would still show an extension
This is called inelastic deformation

Question 25

By overstretching the spring we have reached _______

Answer 25

By overstretching the spring we have reached the limit of proportionality

Question 26

How to calculate the spring constant using the graph

Answer 26

Gradient = change in y/change in x = ___/___ = ___ = e/f

Spring constant = f/e = 1/gradient = 1/__ = ___

Question 27

The spring constant will be the same for any part of the graph as long as we do not exceed the limit of proportionality

Question 28

How to calculate the work done in a spring

Answer 28

Ee = 1/2ke^2

Question 29

What does the area under the force-extension graph equal

Answer 29

The energy in the elastic potential energy store of a stretched spring is equal to the area under a force-extension graph up to the point of the limit of proportionality

Question 30

state Hooke’s law

Answer 30

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

Question 31

How to calculate extension

Answer 31

Extension = final length - original length

Question 32

Define limit of proportionality

Answer 32

The point beyond which the force applied to an elastic object is no longer directly proportional to the extension of the object