Work and Energy

Question 1

What is the formula for work?

Answer 1

Work = Force × Distance

Question 1

What are the units of work?

Answer 1

Joules (J) or Newton-meters (Nm)

Question 2

What is the relationship between energy and work?

Answer 2

Energy is the capacity to do work; work and energy are equivalent.

Question 3

What is Gravitational Potential Energy (GPE), and what is its formula?

Answer 3

GPE is the energy an object has due to its height. Formula: GPE = mgh

Question 4

How can GPE be increased?

Answer 4

By increasing mass or height.

Question 5

What is Kinetic Energy (KE), and what is its formula?

Answer 5

KE is the energy due to motion.
Formula: KE = ½ m v²

Question 6

What are some other forms of energy?

Answer 6

• Elastic potential energy (due to change in shape)
• Chemical energy (stored in chemical compounds)
• Thermal/Heat energy (lost due to friction)
• Nuclear energy (from radioactive elements)
• Solar energy (from the Sun’s light)
• Electric energy (due to charges)

Question 7

What is the law of conservation of energy?

Answer 7

Energy cannot be created nor destroyed, only transformed from one form to another

Question 8

How can we calculate velocity when only given height?

Answer 8

v = √(2gh)

Question 9

What happens to kinetic energy when an object hits the ground?

Answer 9

• If it stops immediately, all KE is lost as heat and sound.
• If it rebounds, some KE is lost as heat and sound.

Question 10

How does air resistance affect energy?

Answer 10

Some energy is lost as heat and sound due to friction with air.

Question 11

How is energy converted in a pendulum?

Answer 11

• At the highest points: All energy = GPE
• At the lowest points: Energy = KE + GPE

Question 12

How does friction affect a moving bicycle?

Answer 12

Some energy is lost as heat due to friction, reducing the KE at the lowest point.

Question 13

What is power, and what is its formula?

Answer 13

Power is the rate of doing work.
* Power = Work / Time
* Power = Energy / Time
* Power = Force × Velocity

Question 14

What are the units of power?

Answer 14

Watts (W) or Joules per second (J/s)

Question 15

What is efficiency, and how is it calculated?

Answer 15

Efficiency is the ratio of useful output energy to input energy.
* Efficiency = (Useful Output Work / Input Energy) × 100%
* Efficiency = (Useful Output Power / Input Power) × 100%

Question 16

How can we improve efficiency?

Answer 16

• Increase useful output energy
• Reduce wasted energy
• Use less input for the same result

Question 17

What are common examples of fossil fuels?

Answer 17

Coal, natural gas, oil, and petrol.

Question 18

What is one advantage of using fossil fuels for electricity?

Answer 18

They provide a high output of energy and can generate electricity continuously.

Question 19

What are two disadvantages of fossil fuels?

Answer 19

They are non-renewable and cause pollution (including acid rain and global warming).

Question 20

How do nuclear fuels generate electricity?

Answer 20

Through nuclear fission, which produces heat to create steam that drives a turbine connected to a generator.

Question 21

Name one advantage of nuclear power.

Answer 21

It offers a very high output of energy and continuous generation of electricity.

Question 22

Name one disadvantage of nuclear power.

Answer 22

It requires strict safety measures and produces dangerous nuclear waste.

Question 23

Which energy sources typically use thermal power stations?

Answer 23

Fossil fuels and nuclear fuels.

Question 24

How do thermal power stations produce electricity?

Answer 24

They burn fuel or use nuclear reactions to boil water, producing steam that turns a turbine connected to a generator.

Question 25

How is geothermal energy converted to electricity?

Answer 25

Water is heated by hot rocks deep underground, creating steam that drives a turbine and generator.

Question 26

Give two advantages of geothermal energy.

Answer 26

It is renewable and has no direct fuel costs.

Question 27

Give two disadvantages of geothermal energy.

Answer 27

Limited suitable locations and the high cost/difficulty of deep drilling.

Question 28

How do hydroelectric and tidal power stations generate electricity?

Answer 28

They use the potential energy of water (falling or tidal) to drive turbines connected to generators.

Question 29

What is one advantage of hydroelectric or tidal power?

Answer 29

They are renewable and have no fuel costs.

Question 30

What is one disadvantage of hydroelectric or tidal power?

Answer 30

They can be expensive to build and may cause environmental damage.

Question 31

How is wind energy converted into electricity?

Answer 31

The kinetic energy of moving air turns turbine blades, which drive a generator.

Question 32

Name one advantage of wind energy.

Answer 32

It is clean, renewable, and has no fuel cost.

Question 33

Name one disadvantage of wind energy.

Answer 33

It provides relatively low output and requires a large, consistently windy area.

Question 34

How do solar panels generate electricity?

Answer 34

They convert sunlight (light energy) directly into electrical energy.

Question 35

What is one advantage of solar energy?

Answer 35

It is renewable, clean, and requires no fuel cost.

Question 36

What is one disadvantage of solar energy?

Answer 36

It depends on weather/sunlight availability and can be expensive

Question 37

How can wave energy be used to produce electricity?

Answer 37

The kinetic energy of ocean waves can drive turbines connected to generators.

Question 38

Why is wave energy not widely used?

Answer 38

It’s often less efficient, location-specific, and can be technologically challenging or expensive.

Question 39

How does biomass generate electricity?

Answer 39

The chemical energy in organic materials (like wood or waste) is released by burning, producing steam to drive a turbine and generator.

Question 40

What is the difference between renewable and non-renewable energy sources?

Answer 40

Renewable sources do not run out (or can be used repeatedly), while non-renewable sources are finite and eventually deplete.

Question 41

Which power station does not use any moving parts to generate electricity?

Answer 41

Solar panels

Question 42

Name three energy sources that do not originate from the Sun.

Answer 42

Nuclear fission, geothermal, and tidal.

Question 43

What is linear momentum, and what is its formula?

Answer 43

Momentum is mass × velocity. Formula: **P = m × v**

Question 44

What are the units of momentum?

Answer 44

kg·m/s

Question 45

How do we calculate the change in momentum?

Answer 45

* If momentum is in the same direction: ΔP = mv - mu * If momentum is in opposite directions: ΔP = mv + mu

Question 46

How is force related to change in momentum?

Answer 46

F = ΔP / t or F = m (v - u) / t

Question 47

What is impulse?

Answer 47

Impulse is equal to change in momentum (ΔP) or Force × Time of contact

Question 48

What does the law of conservation of momentum state?

Answer 48

Total momentum before a collision = Total momentum after a collision

Question 49

What are the types of collisions?

Answer 49

* Elastic collision: KE is conserved **(m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂)** * Perfect inelastic collision: Objects stick together; KE is lost **(m₁u₁ + m₂u₂ = v(m₁ + m₂)**)

Question 50

How does conservation of momentum apply to rockets?

Answer 50

Before launch, momentum is zero. When fuel burns, it produces downward momentum equal to the rocket's upward momentum, making the rocket lift off.

Question 51

How does conservation of momentum apply to a rifle and bullet?

Answer 51

When a bullet is fired forward, the rifle recoils backward with equal but opposite momentum.

Question 52

How is efficiency defined in energy systems?

Answer 52

Efficiency is the ratio of useful output energy (or work) to the input energy, expressed as a percentage: * Efficiency = (Useful output energy / Input energy)×100%

Question 53

What is the relationship between impulse and momentum?

Answer 53

Impulse, defined as force multiplied by the time of contact (Impulse = F × t), equals the change in momentum of an object (ΔP). Momentum is a vector quantity given by mass times velocity.