All simple machines fit into which two families (or types)?
List the 3 machines that are considered levers
List the6 types ofsimple machines.
List 2 ways a screw is a wedge.
Identify 3 simple machines used in the Rube Goldberg machine.
Give the formula for work.
Give the unit of measure for work.
In an ideal machine how is work in related to work out?
How do machines affect work?
Calculate the work required to move a 3500 N crate a distance of 20 m.
What is the formula for mechanical advantage?
How would you calculate the ideal mechanical advantage of a lever?
How would you calculate the ideal mechanical advantage of an incline plane (or wedge)?
A worker applies an effort force of 20 N with a crowbar to pry open a window with a resistance force of 500 N. What is the mechanical advantage of the crowbar?
Calculate the ideal mechanical advantage of a unicycle with a wheel radius of 30 cm and an axle radius of 1.5 cm.
What is the formula for efficiency of a machine?
How would you calculate efficiency when only force and distance (not work) are known?
In practice, machines are never 100% efficient. Why is work out always less than work in?
Calculate the efficiency of a machine that does 300J of work when running but requires an input of 500J of work to operate.
A box weighting 3000N must be place in a truck 1.5 m off the ground. A worker used a force of 600 N to push it up a ramp with a length of 10 m. What is the efficiency of the incline plane?
What is the formula for power?
What is the unit of measure for power?
You are comparing two snowblowers. Both will put of the same amount of work, but the work is done at different rates. Which machine will have the greatest power?
How much power does a person weighing 500 N need to climb a 4m ladder in 5 seconds?
A 600 N passenger is inside a 23,400 N elevator that rises 30 m in exactly 90 seconds. How much power is needed to raise the elevator?
levers and wedges
lever, pulley, wheel and axle
lever, pulley, wheel and axle, wedge, incline plane, screw
Threads are spiraled incline plane and point is wedge
varies
Work = force x distance
Joules
work in = work out
Work is not affected, only force and distance
3500 N x 20 m = 70000J
Mechanical Advantage = Resistance Force/ Effort Forct
IMA = effort arm length/ resistance arm length
IMA = effort distance/ resistance distance = length of slope/ height (or width) of slope
MA = 500N/ 20N = 25
IMA = wheel radius/ axle radius = 30 cm/ 1.5 cm
Efficiency = (Work out/ Work in) x 100%
Efficiency = Resistance Force x Resistance distance/ Effort force x effort distance
Some work is always converted to heat due to friction.
efficiency = 300J /500J x 100% = 60%
efficiency = (3000N x 1.5m)/ (600N x 10m) x 100% = 75%
Power = Work / Time
Watts
The machine with the fastest rate.
Power = 500N x 4m/ 5 seconds = 400W
Power = (600n + 23,400N) x 30m/ 90 s = 8000W = 8 kW
