4c Work and power

Question 1

What does ‘Doing work’ mean?

Answer 1

• Transferring energy (using a force)
• Work done = energy transferred

Question 2

What is the equation for work?

Answer 2

Work = Force x Distance moved (in direction of force)
W = F x d
Units:
Work - J
Force - N
Distance - m

Question 3

What is the equation for Gravitational Potential Energy (GPE)?

Answer 3

GPE = mass x gravitational field strength (g) x height
GPE = m x g x h
Units:
GPE - J
mass - kg
g - W/kg (m/s2)
height - m

Question 4

What is the equation for Kinetic energy (KE)?

Answer 4

KE = 1/2 x mass x speed2
KE = 1/2 x m x v2
Units:
KE - J
Mass - kg
speed - m/s

Question 5

How does conservation of energy produce a link between gravitational potential energy, kinetic energy and work?

Answer 5

The conservation of energy produces a link between gravitational potential energy, kinetic energy and work. For example, when a ball is dropped, gravity does work on it and its gravitational potential energy becomes kinetic energy as it accelerates downwards

Question 6

What can power be described as?

Answer 6

Power is the rate at which energy is transferred or the rate at which work is done. For
example, a lamp with a greater power will be brighter because it transfers more energy from
electrical energy to light and heat energy in a given time.

Question 7

What is the equation for power?

Answer 7

Power = work done / time taken
Or Energy transferred = work done / time taken
P = W/t
Units:
Power = W
Work done = J
time = s