1 - work energy and power

Question 1

work done

Answer 1

force applied to alter the motion of position of an object
= Fs (force * displacement)
unit is Joule
displacement must be in the direction of the force

Question 2

KE

Answer 2

energy possessed y motion
1/2mv^2

Question 3

how to derive KE eq

Answer 3

use v62 = u^2 + 2as and rearrange to get a = 1/2s v^2
F = ma F = 1/2s mv^2
then W = Fs
so W = 1/2 mv^2

Question 4

work done while there is also a resistive force (R)

Answer 4

Fs - Rs = change in KE
(F-R)s = change in KE

Question 5

work energy principle

Answer 5

net work done by all the forces acting on a body is equal to the change in kinetic energy of the body
= 1/2 m (v^2 - u^2)

Question 6

GPE

Answer 6

mgh
energy dependent on the position of an object in a gravitational field

Question 7

work done in terms of KE and GPE

Answer 7

W = change in KE + change in GPE
(work done by external forces other than W)

Question 7

mechanical energy

Answer 7

GPE
KE
elastic potential

Question 8

principle of conservation of mechanical energy

Answer 8

if there is no W by external forces other than the force of gravity the sum of potential energy and KE is constant
W = change in KE + change in GPE (where W = 0)
final mech energy = initial mech energy

Question 9

WD on an angle

Answer 9

= F cosθ s

Question 10

power

Answer 10

rate of work done
= WD/t = Fs/t
= Fv (tractive force * speed)
unit is Watt
1J/s= 1W