Work Energy and Power

Question 1

Work done

Answer 1

when an object is moved over a distance by an external force applied in the direction of displacement

work done = force x displacement

• when work is done, object transfers energy

Question 2

Principle of conservation of energy

Answer 2

energy cannot be created nor destroyed, it can only change from one form to another

• the amount of energy in a closed system stays constant

Question 3

Energy dissipates

Answer 3

any energy not transferred to useful energy is wasted as it is lost to surroundings

Question 4

Efficiency

Answer 4

the ratio of useful energy output from the system to the total energy input

efficiency = useful energy output / total energy input x 100%

Question 5

Power

Answer 5

the rate at which an object transfers energy / work done per unit time

P = E / t = W / t

Question 6

Moving power equation

Answer 6

P = Fv

Question 7

Factors for moving power

Answer 7

• constant force
• constant velocity

Question 8

Gravitational potential energy

Answer 8

energy stored in a mass due to its position in a gravitational field

△GPE =mg △h

Question 9

Kinetic energy

Answer 9

energy of an object due to its motion

KE = 1/2mv^2

Question 10

How is work done in GPE

Answer 10

When a heavy object is lifted, work is done since the object is provides with an upward force against the downward force of gravity — energy transfers

Question 11

How is work done in KE

Answer 11

Work is done when an object accelerates due to force — energy is transferred to the object