5: WEP

Question 1

Define Work Done

Answer 1

Work Done by a force on the body is equal to the product of the force on the body and the displacement in the direction of the force.

Question 2

1. Equation of work done by expanding gas + assumption
2. How to obtain graphically work done by expanding gas

Answer 2

1. W = pressure x change in volume, assume that pressure remains constant
2. Area under pressure volume graph is work done

Question 3

Proof EPE

Answer 3

EPE = (1/2)Fx = (1/2)(kx)x = (1/2)kx^2

Question 4

Proof GPE = mgh

Answer 4

1. By N3L, Ext Force = mg
2. WD = F x h = mgh

Option 2: Via U = GMm/r

Question 5

Proof KE = (1/2)mv^2

Answer 5

WD = Fs = mas = m(1/2)(v^2-u^2) = (1/2)m(v^2- u^2)

Question 6

Define Principle of conservation of energy

Answer 6

POCOE states that energy cannot be destroyed but can be transformed into other forms of energy

Question 7

Define Efficiency

Answer 7

Efficiency is the ratio of useful energy output to the total energy input

Question 8

Define power + eqns

Answer 8

Power is the rate of work done/energy transfer
P = WD/t = Fs/t = Fv