Topic 11 - Work and Energy

Question 1

What is a system?

Answer 1

An object or group of objects.

Question 2

What are the different ways energy can be stored in a system?

Answer 2

Kinetic store, gravitational potential store, chemical store, elastic potential store, nuclear store and internal store

Question 3

What is a kinetic store?

Answer 3

The energy stored by an object’s movement.

Question 4

What is a gravitational potential store?

Answer 4

The energy stored in objects raised above the Earth’s surface, due to the Earth’s gravitational field.

Question 5

What is a chemical store?

Answer 5

The energy stored by the chemical bonds between atoms.

Question 6

What is an elastic potential store?

Answer 6

The energy stored when an object is being stretched, compressed or squashed.

Question 7

What is a nuclear store?

Answer 7

The energy stored in the nucleus of an atom that can be released by radioactive decay.

Question 8

What is an internal store?

Answer 8

Sum of the kinetic energy stored in the particles of an object and the chemical energy stored in chemical bonds between particles in the object.

Question 9

What is the equation for kinetic energy?

Answer 9

1/2 x mass x velocity2

Question 10

What is the equation for the change in GPE?

Answer 10

Mass x gravitational field strength x change in height

Question 11

What is energy measured in?

Answer 11

Joules

Question 12

What is the equation for elastic potential energy?

Answer 12

1/2 x spring constant x extension2

Question 13

What is the spring constant measured in?

Answer 13

N/m

Question 14

What is the extension measured in?

Answer 14

Metres

Question 15

What is the conservation of energy?

Answer 15

Energy cannot be created or destroyed, only transformed

Question 16

How can energy be transformed?

Answer 16

Electrical work, heating, waves, mechanical work

Question 17

What is electrical work?

Answer 17

When an electrical current transfers energy from one object to another.

Question 18

How does heating transform energy?

Answer 18

Heating an object increases its internal energy.

Question 19

How do waves transform energy?

Answer 19

Light and other types of waves can transfer energy from one object to another.

Question 20

What is mechanical work?

Answer 20

When energy transferred from one object to another via a force.

Question 21

What is the equation for work done?

Answer 21

Force x distance (moved along the line of action of the force)

Question 22

How can more work be done?

Answer 22

Applying the same force over a longer distance, apply a larger force for the same distance.

Question 23

What is work?

Answer 23

Total change in energy of/energy transferred to an object.

Question 24

What is on the x-axis of an extension-load graph?

Answer 24

The extension of the spring

Question 25

What is on the y-axis of an extension-load graph?

Answer 25

The force acting on the spring

Question 26

What is a limit of proportionality?

Answer 26

When an object will not return to its original length when the force is removed.

Question 27

What is extension directly proportional to?

Answer 27

The force applied

Question 28

What happens if a spring is over-stretched?

Answer 28

It will not return to its original length

Question 29

What relationship do spring constant and spring stiffness have?

Answer 29

The higher the spring constant, the stiffer the spring.

Question 30

What is Hooke's Law?

Answer 30

Force = spring constant x extension

Question 31

Which letter is used to represent extension?

Answer 31

e or x

Question 32

Which letter is used to represent spring constant?

Answer 32

k

Question 33

Investigating Hooke's Law 1

Answer 33

First, measure the original length of the spring.

Question 34

Investigating Hooke's Law 2

Answer 34

Next, hang different masses on the spring and measure the length of the spring in each case.

Question 35

Investigating Hooke's Law 3

Answer 35

Adding masses to the spring increases the downwards force as each mass has weight.

Question 36

Investigating Hooke's Law 4

Answer 36

The extension of the spring equals the length with masses minus the original length.

Question 37

Investigating Hooke's Law 5

Answer 37

Plot a graph with extension of the spring on the x axis and force on the y axis.

Question 38

How can the extension of the spring be worked out in an investigation?

Answer 38

Length of the loaded spring − natural length of the spring

Question 39

What apparatus is needed to investigate Hooke's Law?

Answer 39

A spring, a ruler and a known mass

Question 40

What happens when a spring is compressed?

Answer 40

Elastic potential energy is stored in the spring (so long as a spring isn’t inelastically deformed).

Question 41

What is the elastic potential energy stored in a stretched spring equal to?

Answer 41

The work done when stretching it

Question 42

What does the area under a force-extension graph show?

Answer 42

The elastic potential energy stored in a stretched spring

Question 43

What is the equation for percentage efficiency?

Answer 43

Useful energy output/total energy output x 100

Question 44

How could the energy efficiency of a toy car be increased?

Answer 44

Improve aerodynamics and lubricate the track

Question 45

Why does lubrication increase energy efficiency?

Answer 45

It reduces frictional forces, reducing dissipated energy

Question 46

Why does aerodynamicising the car increase energy efficiency?

Answer 46

It reduces the effects of air resistance.