P5 Flashcards
1
Q
Work done
A
W = fd or work done = energy transferred
Thus power = fd/t or fv
2
Q
Work done at an angle to motion
A
e.g pushing a toy car from diagonally above
solved by W = F cosθ
3
Q
Principle of conservation of energy
A
total energy of closed system stays constant, can transfer but not create or destroy
4
Q
ke and gpe
A
ke is energy due to motion - 0.5kx2
gpe is capacity to do work due to position in gravity field - mgh
gpe often converted to ke or vice versa
so v = root 2gh
5
Q
deriving kinetic energy equation
A
ke = W
W = fd
W = mad
W = mav2/2a (as u = 0)
= mv2/2
= 1/2 mv2
6
Q
Power
A
rate of work done (J/s or W)
P = W/t
or P = fv
7
Q
Efficiency
A
useful output energy/ total input energy x 100
