| Machines |
| #1 |
All simple machines fit into which two families (or types)? |
levers and wedges |
| #2 |
List the 3 machines that are considered levers |
lever, pulley, wheel and axle |
| #3 |
List the6 types ofsimple machines. |
lever, pulley, wheel and axle, wedge, incline plane, screw |
| #4 |
List 2 ways a screw is a wedge. |
Threads are spiraled incline plane and point is wedge |
| #5 |
Identify 3 simple machines used in the Rube Goldberg machine.  |
varies |
| Mechanical Advantage |
| #1 |
What is the formula for mechanical advantage? |
Mechanical Advantage = Resistance Force/ Effort Forct |
| #2 |
How would you calculate the ideal mechanical advantage of a lever? |
IMA = effort arm length/ resistance arm length |
| #3 |
How would you calculate the ideal mechanical advantage of an incline plane (or wedge)? |
IMA = effort distance/ resistance distance = length of slope/ height (or width) of slope |
| #4 |
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? |
MA = 500N/ 20N = 25 |
| #5 |
Calculate the ideal mechanical advantage of a unicycle with a wheel radius of 30 cm and an axle radius of 1.5 cm. |
IMA = wheel radius/ axle radius = 30 cm/ 1.5 cm |
| Efficiency |
| #1 |
What is the formula for efficiency of a machine? |
Efficiency = (Work out/ Work in) x 100% |
| #2 |
How would you calculate efficiency when only force and distance (not work) are known? |
Efficiency = Resistance Force x Resistance distance/ Effort force x effort distance |
| #3 |
In practice, machines are never 100% efficient. Why is work out always less than work in? |
Some work is always converted to heat due to friction. |
| #4 |
Calculate the efficiency of a machine that does 300J of work when running but requires an input of 500J of work to operate. |
efficiency = 300J /500J x 100% = 60% |
| #5 |
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? |
efficiency = (3000N x 1.5m)/ (600N x 10m) x 100% = 75% |
| Power |
| #1 |
What is the formula for power? |
Power = Work / Time |
| #2 |
What is the unit of measure for power? |
Watts |
| #3 |
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? |
The machine with the fastest rate. |
| #4 |
How much power does a person weighing 500 N need to climb a 4m ladder in 5 seconds? |
Power = 500N x 4m/ 5 seconds = 400W |
| #5 |
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? |
Power = (600n + 23,400N) x 30m/ 90 s = 8000W = 8 kW |
