1. WORK AND POWER
WORK AND POWER

2. Work- when a force is applied over a distance in the direction of the motion. Scalar quantity
Work = Force x distance
W = Fd
Unit: Nm or Joule (J)

3. Ex 1: A 40kg cart is rolled along the floor by a horizontal force at a constant velocity. If 150N is applied to the cart for 10m, how much work is done? W = Fd W = 150N( 10m) W= 1500J
F = 150N

4. Ex 2: A sailor pulls a boat along a dock for 30m with a force of 250N
Ex 2: A sailor pulls a boat along a dock for 30m with a force of 250N. What work is done if the rope is held at 60° with respect to the water? Fp = F cosѲ Fp = 250N cos 60° Fp = 125N 60° W = Fp d W= 125N(30m) W= 3750 J Fp

5. SIMPLE MACHINES a) Redirects the applied force b) Breaks job up into smaller repetitions
Levers Pulleys Gears wedge wheel and axel

6. Work input Work output - Work done by a machine.
Work input -work done to operate the machine.
%Efficiency = Work output x 100
Work input
Ex: A pulley system lifts a 90N crate 3m up. If a man applies 30N of force for a length of 15m, what is the efficiency of the pulley system?
%E = (90N)(3m) x100 = 60% efficient
(30N)(15m)
Where did the other 40% go?

7. POWER- The rate of doing work
Power = Work
time
P= W/t = (Fd)/t = Fv
Unit: J/s or watt (W)
*English unit= horse power (746 watts)*

8. Ex: A machine produces a force of 40N over a distance of 100m
Ex: A machine produces a force of 40N over a distance of 100m. If it does this in 5.0 seconds, what is the power of the machine in watts and kilowatts? P = Fd/t P = 40N( 100m) 5.0 sec P= 800 W P = 0.80 kW