Work and Power
This is what happens when a force makes an object move in the direction of the force.
What is work?
Besides the size of a force and the distance it acts, a machine can change this about a force.
What is direction?
A flat surface with one end higher than the other, like a ramp.
What is an inclined plane?
A knife blade or an axe head is this simple machine.
What is a wedge?
This is the rate at which work is done.
True or false: a machine reduces the amount of work you have to do.
What is false? (It makes work easier but doesn’t decrease the work.)
The fixed point a lever pivots on.
What is the fulcrum?
The rope system used to raise a flag.
What is a pulley?
The units used to measure work and power, in that order.
What are joules and watts?
The force you apply to a machine is called this.
What is the input force (effort force)?
A wheel attached to a smaller rod that turns with it, like a doorknob.
What is a wheel and axle?
A seesaw is an example of this simple machine.
What is a lever?
A student pushes as hard as she can against a wall, but the wall doesn’t move. The amount of work she does.
What is zero (no work, because there is no movement)?
This is the number of times a machine multiplies your input force.
What is mechanical advantage?
An inclined plane wrapped around a cylinder, like a jar lid or a bolt.
What is a screw?
A bicycle, which combines several simple machines, is this type of machine.
What is a compound machine?
A student lifts a box with a 20 N force over 3 meters in 5 seconds. Her power.
What is 12 watts? (20 N × 3 m = 60 J, then 60 J ÷ 5 s)
A machine takes a 10 N input force and produces a 50 N output force. Its mechanical advantage.
What is 5? (50 ÷ 10)
The number of simple machines, and any three of them.
What are six: lever, pulley, wheel and axle, inclined plane, wedge, screw?
Pushing a box up a longer ramp takes less force than a shorter one because the force acts over this.
What is a greater distance? (Work stays the same, so more distance means less force.)