Definitions
The transfer of energy that occurs when a force is applied over a distance
Work
Output force/ input force
Mechanical advantage
A simple machine made up of a bar that pivots, or rotates, about a fixed point called a fulcrum
Lever
The ratio of a machines output force produced to the input force applied
Mechanical advantage
A motor applies 5000 N force and raises an elevator 10 stories. If each story is 4 m tall. How much work does the motor do?
200,000 J
The rate at which work is done
Power
Force X Distance
Work
An axle attached to the center of a wheel and both rotate together
Wheel and Axle
Radius of wheel/ radius of axel
Wheel and Axle
A pulley system uses a 250 N force to lift a 2,750 N crate. What is the mechanical advantage of the system?
11
Any device that makes doing work easier
Machine
Work/Time
Power
A flat sloped surface
Inclined Plane
Length of inclined plane/ height of inclined plane
Inclined Plane
An assembly line machine needs 150 J of input work to do 90 J of output work. What is the efficiency of the machine?
60%
What are the three ways machines make doing work eaiser?
Change the size of the force
Change the direction of the force
Change the Distance of the force
Output work/Input work
Efficiency
A simple machine that is a grooved wheel with a rope or cable wrapped around it
A pulley
Length of input arm/ Length of output arm
Lever
What is the mechanical advantage of a screwdriver with a 24 mm radius handle and an 8 mm radius shaft?
3
The ratio of a machine's output work to the input work
Efficiency
Efficiency of machine 1 X efficiency of machine 2 X efficiency of machine 3
Efficiency of compound machines
What are the three types of levers?
First class, second class, third class
Why does friction decrease the efficiency of a machine?
Converts energy into thermal energy which is lost to the system
How much power is used when 600 J of work is done in 10s?
60 W