Work, Energy and Power. Work. W = Fs W= work F = force s = displacement Whe a force makes an object move, work has been done. Whenever work is done, energy is transferred form one place to another or transformed from one form to another. Units are = 1Nm = 1J(joule). Practice Problem 1.
W = Fs
There are lots of different forms of energy.
speed and mass
result of its position
At a railway station, two trains slowly collide in order to “couple” (join together). If one train of mass 12000kg is moving at 0.75m/s and the other of mass 3000kg is stationary, calculate the velocity of the two as they move away.
We already solved this for .6m/s. Now tell me the kinetic energies before and after the collision.
PART A: His feet will stop when they hit the ground but his body will still be travelling forward at the bike speed, so he will fall over forwards.
PART B: 4m/s
PART C: before – 250J
after – 400J
The increase in KE is due to energy provided or work done by the boy pushing on the bicycle.
Remember: P = W/t
Quick review: what is work?
Quick review: what is velocity?
The SI unit of power is the watt.
Horsepower is also a unit.