3.3 Work, energy and power

Question 1

What is the principle of conservation of energy?

Answer 1

Energy cannot be created or destroyed. Energy can be transferred from one form to another but the total amount of energy in a closed system will not change

Question 2

Define the joule

Answer 2

One joule is the work done when a force of 1 newton over an object through a distance of 1 metre

Question 3

Derive the equation for kinetic energy:

Answer 3

Change in kinetic energy of an object equals work done so Ek=Fx
F=ma
a=(v-u)/t
x=average v . t= (u+v)t/2
Ek=max=m . (v-u)/t . (u+v)/2 . t
Cancel the t’s and expand brackets give you a slightly more familiar Ek=1/2mv^2 - 1/2mu^2
Sub in u=0, the object has no kinetic energy
Ek=I/2mv^2

Question 4

Transfer of energy is eqaul to

Answer 4

workdone

Question 5

Kinetic energy

Answer 5

1/2mv^2

Question 6

Gravitational energy

Answer 6

mgh

Question 7

work done by force

Answer 7

W=Fxcos(theta)

Definition: Force X Distance moved in direction of the force

Question 8

derive P=Fv from first principles

Answer 8

p=wd/t
wd=Fx
so
P=Fx/t
but v=x/t sub into above equation