Chapter 5 - Work, Energy and Power

Question 1

Define Work Done

Answer 1

Work done is defined as force in same direction motion (newtons) multiplied by the distance moved (m), measured in joules.
W = Fx
If the force applied is at an angle you will need to resolve for the component parallel to the motion.

Question 2

Define Power.

Answer 2

Power is defined as the work done per second. Measured in Watts.
P = W / t

Question 3

Define a Watt.

Answer 3

A watt is defined as the rate of energy transfer, 1 watt is 1 joule per second.

Question 4

How can Power be expressed in terms of velocity?

Answer 4

P = W/t
P = Fx/t
P = Fv
This equation links power and velocity.

Question 5

How can change in Kinetic energy be defined from the work done equation?

Answer 5

W = Fx
F = ma
W = max
a = (v-u)/t and x = (v+u)t/2
W = m x (v-u)/t x (v+u)t/2
W = 1/2 x m x (v-u) x (v+u)
W = 1/2mv^2 - 1/2mu^2
Change in kinetic energy = 1/2m(change in V)^2

Question 6

Define Gravitational Potential Energy.

Answer 6

Gravitational potential energy is the energy of an object die to its position in a gravitational field. 
Ep = mgh
m - Mass (kg)
g - gravity
h - height (m)

Question 7

What is the Principle of Conservation of Energy?

Answer 7

The Principle of Conservation of energy states that energy cannot be created or destroyed only transferred to a different form.
Energy in a closed system will not change.
Energy in = Energy out

Question 8

What is the equation for efficiency?

Answer 8

Efficiency = (Useful output energy / Total input energy) x 100