Work and Power
This is the force exerted on an object that causes it to move.
work
This is a device that changes the amount of force exerted, the distance over which a force is exerted, or the direction over which a force is exerted.
machine
This is the most basic device for making work easier; these are the small building blocks for making complex machines.
simple machine
This is a simple machine that consists of a grooved wheel with a rope or cable wrapped around it.
pulley
This is when a small input force is exerted over a long distance. This lever makes this possible.
inclined plane
This is the rate at which one form of energy is transferred to another.
power
This is the force exerted ON a machine.
input force
This is a simple machine that is a flat, slopped surface.
inclined plane
This is a simple machine that consists of two attached circular or cylindrical objects, that rotate around a common axis, each one with a different radius.
wheel and axle
An inclined plane make loading a heavy crate onto a truck easier than lifting the crate. This happens because it reduces the force you exert on this.
crate
This is the unit of power when one joule of work is done in one second.
watt
This is the force exerted on an object BY a MACHINE.
output force
This is a simple machine that is an inclined plane wrapped around a central cylinder to form a spiral.
screw
This is a device that combines two or more simple machines.
compound machine
This changes the direction of the force but not the size of the object.
fixed pulley
How much work, in joules, do you do when you push a shopping cart with a force of 50 N for a distance of 5 m?
250 J
This is the mechanical advantage for a machine.
output force : input force
These are three closely related simple machines in the inclined plane family.
wedge, screw, inclined plane
You exert a 100-N force on a pulley system to lift 300 N. This is how many sections of rope support the weight.
3
This simple machine is made of a grooved wheel with a rope or cable wrapped around it.
pulley
You're holding your dog's leash as the dog pulls on the leash at an angle to the ground. You move forward. What fraction of the dog's force does work on you?
The part of dog's force that acts in the horizontal direction
This is why real machines have an efficiency of less than 100%.
friction
This is the ideal mechanical advantage of a lever with 2.0 m between the input force and the fulcrum and 1.0 m between the output force and the fulcrum.
2.0
A pencil sharpener is made from a wheel and axle with an ideal mechanical advantage of 3 and a wedge with an ideal mechanical advantage of 4. This is the overall ideal mechanical advantage of the pencil sharpener.
12
This type of pulley does not change the direction of the force applied.
moveable pulley