Work, Power, and Simple Machines

Power Equation

P=W/t, if W=work and t=time

perfect machine

The output work equals exactly the input work. This is impossible due to friction. Therefore, output work is always less than input work, and can never be more than it.

Work Equation

W=Fd, if F=force and d=distance

machine

a device with moving parts that work together to accomplish a task.

work

a form of energy that comes from force applied over distance. A force of 1 newton does 1 joule of work when the force causes 1 meter of motion in the direction of the force.

watt

a power of 1 joule per second.

horsepower

a unit of power equal to 746 watts

simple machine

an unpowered mechanical device that accomplishes a task with only one movement.

Efficiency Equation

e=o/i, if o=output work and i=input work

input

forces, energy, or power supplied to make a machine work.

Gear Ratio Equation

g=o/i if o=output work and i=input work

output

the forces, energy, or power provided by the machine.

power

the rate of doing work or moving energy. Power is equal to energy (or work) divided by time.

mechanical advantage

the ratio of output force divided by input force.

efficiency

the ratio of output work divided by input work. Efficiency is often expressed as a percent with a perfect machine having 100 percent efficiency. You can improve efficiency by decreasing friction.