P1

Question 1

What is energy?

Answer 1

The ability to do work.

Question 2

What unit is energy measured in?

Answer 2

Joules (J).

Question 3

What is work done?

Answer 3

When a force causes an object to move through a distance.

Question 4

Equation for work done?

Answer 4

Work done = force × distance

Question 5

Name the 8 energy stores.

Answer 5

1. Kinetic
2. Thermal (internal)
3. Chemical
4. Gravitational potential
5. Elastic potential
6. Nuclear
7. Magnetic
8. Electrostatic

Question 6

Which store does a moving object have?

Answer 6

Kinetic energy.

Question 7

Which store increases when an object heats up?

Answer 7

Thermal (internal) energy.

Question 8

Equation for kinetic energy?

Answer 8

KE = ½ × mass × speed²

Question 9

What happens to kinetic energy if speed doubles?

Answer 9

It increases by 4 times.

Question 10

What is gravitational potential energy?

Answer 10

Energy an object has due to its height above the ground.

Question 11

Equation for GPE?

Answer 11

GPE = mass × gravity × height

Question 12

What is the value of gravity (g) on Earth?

Answer 12

9.8 N/kg (often rounded to 10 N/kg in exams).

Question 13

When does an object store elastic potential energy?

Answer 13

When it is stretched or compressed (e.g. a spring).

Question 14

Equation for elastic potential energy?

Answer 14

E = ½ × spring constant × extension²

Question 15

How can energy be transferred?

Answer 15

. Mechanically
. Electrically
. By heating
. By radiation (e.g. light, infrared)

Question 16

What happens to energy when it is transferred?

Answer 16

It is conserved, but spread out (often less useful).

Question 17

What is the law of conservation of energy?

Answer 17

Energy cannot be created or destroyed, only transferred.

Question 18

Why do devices seem to “lose” energy?

Answer 18

Energy is transferred to thermal energy of surroundings.

Question 19

What is efficiency?

Answer 19

How much useful energy or power is produced compared to the total input.

Question 20

Equation for efficiency (energy)?

Answer 20

Efficiency = useful energy output ÷ total energy input

Question 21

How is efficiency often given in exams?

Answer 21

As a percentage (%).

Question 22

What is power?

Answer 22

The rate of energy transfer.

Question 23

Unit of power?

Answer 23

Watts (W).

Question 24

Equation for power?

Answer 24

Power = energy ÷ time

Question 25

What is the energy efficiency practical about?

Answer 25

Investigating how insulation affects energy transfer.

Question 26

What does insulation do to energy transfer?

Answer 26

Reduces energy loss to the surroundings.

Question 27

What happens to energy when a system changes?

Answer 27

Energy is transferred between stores, but the total energy remains constant.

Question 28

What is meant by a “closed system”?

Answer 28

A system where no energy enters or leaves.

Question 29

In a falling object, which energy stores change?

Answer 29

Gravitational potential energy decreases and kinetic energy increases.

Question 30

Why does energy often end up in thermal stores?

Answer 30

Due to friction and air resistance.

Question 31

What must happen for work to be done?

Answer 31

A force must cause an object to move.

Question 32

What happens if the force is perpendicular to motion?

Answer 32

No work is done.

Question 33

Why does friction reduce efficiency?

Answer 33

It transfers energy to unwanted thermal stores.

Question 34

Which variables affect kinetic energy?

Answer 34

Mass and speed

Question 35

How does kinetic energy change if mass doubles?

Answer 35

Kinetic energy doubles.

Question 36

Why is speed more important than mass in KE calculations?

Answer 36

Speed is squared in the equation.

Question 37

When is the GPE equation valid?

Answer 37

Near the Earth’s surface.

Question 38

What must be the unit of height in the GPE equation?

Answer 38

Metres (m).

Question 39

What happens to GPE if height triples?

Answer 39

GPE triples.

Question 40

What is the spring constant?

Answer 40

A measure of how stiff a spring is.

Question 41

Unit of spring constant?

Answer 41

N/m.

Question 42

When is the elastic potential energy equation valid?

Answer 42

When the spring is within its limit of proportionality.

Question 43

What happens beyond the elastic limit?

Answer 43

The spring will not return to its original shape.

Question 44

How else can power be calculated using force and speed?

Answer 44

Power = force × velocity

Question 45

What does a high power rating mean?

Answer 45

Energy is transferred quickly.

Question 46

Does higher power always mean more energy transferred?

Answer 46

No — it depends on time.

Question 47

Equation for efficiency using power?

Answer 47

Efficiency = useful power output ÷ total power input

Question 48

Why can no device be 100% efficient?

Answer 48

Some energy is always transferred to thermal stores.

Question 49

How can efficiency be improved?

Answer 49

Reduce friction, use lubrication or insulation.

Question 50

What does “dissipated” mean in energy questions?

Answer 50

Spread out into the surroundings, usually as thermal energy.

Question 51

What does “useful energy” mean?

Answer 51

Energy transferred to the desired store.