Booklet 6: Work, Energy and Power

Question 1

Work Done

Answer 1

force x distance moved in the direction of the force
energy transferred

W=Fs
Work (J) = Force (N) * displacement (m)

Question 2

Joule

Answer 2

the amount of work done by a force of 1 Newton acting over a distance of 1 metre in the direction of the force

Question 3

Gravitational Potential Energy

Answer 3

energy of an object due to its position in a gravitational field

Ep=mgh
Gravitational Potential Energy (J) = mass (kg) * gravity (ms^-2) * height (m)

Question 4

Kinetic Energy

Answer 4

energy due to motion of an object with mass

Ek=1/2mv^2
Kinetic Energy (J) = 1/2 * mass (kg) * velocity^2 (ms^-1)

Question 5

Efficiency

Answer 5

efficiency = (useful energy out/total energy in) x 100

since P=E/t ,
efficiency = (useful power out/total power in) x 100

Question 6

Power

Answer 6

rate of work done

P=W/t
Power (W) = Work Done (J) / time (s)