Energy

Question 1

Name the unit for energy and it’s symbol.

Answer 1

Joules J

Question 2

What kind of energy does a sprinter gain as they accelerate?

Answer 2

Kinetic energy (Ek)

Question 3

A snowflake falls. What kind of energy does it lose?

Answer 3

Gravitational potential energy, Ep

Question 4

What is meant by ‘conservation of energy’?

Answer 4

Energy cannot be created or destroyed, it can only change forms. This means the the total energy is conserved.

Question 5

How do you calculate gravitational potential energy?

Answer 5

Change in Ep = mg change in h

Question 6

Find the mass of an object, given gravitational potential energy, change in height and gravity.

Answer 6

m = change in Ep / g x change in height

Question 7

How do you calculate height, given mass and gravitational potential energy?

Answer 7

Change in Ep = mg change in h
So m = change in Ep / g change in h

Question 8

Calculate kinetic energy, given speed and mass.

Answer 8

Change in Ek = 1/2 mv2

Question 9

Calculate mass, given speed and Ek

Answer 9

Change in Ek = 1/2mv2
So m = 2Ek / v2

Question 10

If two runners accelerate to a sprint near the finish line, what happens to their kinetic energy?

Answer 10

Their kinetic energy will increase, as kinetic energy is proportional to speed squared.
Ek = 1/2mv2, so if v increases, Ek also increases.

Question 11

Calculate velocity, given mass and kinetic energy.

Answer 11

Change in Ek = 1/2mv2
So v2 = 2Ek / m
v = square root (2Ek / m)