Topic 8 🔨💪

Question 1

State the law of energy conservation.

Answer 1

Energy cannot be created or destroyed (it can only be transferred into different forms).

Question 2

Describe the energy changes involved when a ball is thrown upwards and then returns to its starting position. Ignore air resistance.

Answer 2

• Upwards: KE is converted to GPE
• Peak: Maximum GPE, zero KE
• Downwards: GPE is converted to KE

Question 3

State any changes in the total energy of a ball that is kicked, assuming that no external forces act.

Answer 3

The total energy of the system remains constant due to the conservation of energy.

Question 4

Describe the energy changes that occur in a filament light bulb.

Answer 4

• Electrical energy is transferred into light and heat energy.
• Light is a useful energy form, heat is waste energy.

Question 5

In what ways can the energy of a system be changed?

Answer 5

• Through work done by forces
• Through electrical input
• Through heating

Question 6

How can energy be changed through work done by forces?

Answer 6

A force which moves an object (kinetic energy) caused work to be done over a distance.

Question 7

What is the definition of ‘Power’?

Answer 7

The rate at which energy is transferred (or rate at which work is done).

Question 8

What is the unit of power?

Answer 8

Watt (W)

Question 9

What is one Watt equivalent to?

Answer 9

1 Joule per second (J/s)

Question 10

What is the equation for work done?

Answer 10

E = F x d

Work Done (J) = Force (N) x distance moved (m)

Question 11

What is the equation for power?

Answer 11

P = E/t

Power (Watts) = work done (J) / time (s)