1
The ratio of output to input force
Mechanical Advantage
M.A. equation:
Force output / Force input
The greater the M.A. of a machine, the _______________ it is to operate.
easier
In ideal machines, work input = work _____.
output
Percentage of useful work produced
efficiency
True or False: Machines cannot be 100% efficient
True
Work done to overcome ____________ is changed into heat.
friction
The ___ goes into the surroundings.
heat
Friction is a _________________ force.
dissipative
As M.A. increases, the Eff of a machine _________________.
decreases
Loss of efficiency is due to ______________.
friction
work done per unit of time
power
formula for power
P = W / t
Unit for power
watt (w)
1 J / S equals one ______
watt
A box weighing 460 N is lifted 12 m straight up in 10 s by a machine. What is the power of the machine?
552 w
formula for efficiency
eff = (work out / work in) x 100
Sara raises a 800 N piano 3.0 m by a system of pulleys. She exerts 200 N of force and pulls 16 m of rope. Calculate the mechanical advantage of the machine.
MA = 800 / 200 = 4
Kevin raises a 800 N piano 3.0 m by a system of pulleys. She exerts 200 N of force and pulls 16 m of rope. calculate the work input.
W input = 200 x 16 = 3200 J
Mary raises a 800 N piano 3.0 m by a system of pulleys. She exerts 200 N of force and pulls 16 m of rope. Calculate work output.
W output = 800 x 3 = 2400 J
Dora raises a 800 N piano 3.0 m by a system of pulleys. She exerts 200 N of force and pulls 16 m of rope. Calculate the efficiency.
2400 / 3200 x 100 = 75 %