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Mechanism
Made up of several different kinds of machines that work together to perform a specific function.
Simple machine
A machine that requires the application of a single force to do work (Eg. You only need pushing force to move a cart into a trick using a ramp).
How do simple machines and mechanisms transfer energy?
THey use forces.
Six Simple Machines
Lever, Inclined plane, Wheel and axle, Screw, Wedge, Pulley.
Lever
A rigid bar that is supported at one point
Fulcrum
The single point that supports a lever.
What are the three classes of levers classified by?
Locations of the fulcrum, the input force, the output force.
First-class lever
Has the fulcrum between the input and output forces. The output force is always in the opposite direction of the input force.
Second class lever
The output force is between the fulcrum and input force.
Third class lever
The input force is between the fulcrum and output force.
IMA of a lever
Pulley
A grooved wheel with a rope looped around it. A pulley can change the direction of the force or increase the output force depending on whether it is fixed or movable.
What do fixed pulleys do?
They change only the direction of the force. A fixed pully has an IMA of 1.
What is a movable pulley?
When one end of the rope is fixed and the pulley can move.
What does a movable pulley do?
A movable pulley is supported by the rope at two locations. At these locations, the tension on the rope applies an upward force on the pulley. The IMA is 2.
The IMA of a pulley
THe IMA of a pulley is equal to the number of support ropes.
What is a support rope?
A segment of rope that applies force on the pulley.
Wheel and axle
An axle that is attached to a large disk called the wheel (Eg. a screwdriver).
IMA of Wheel and Axle
Radius of the wheel divided by the radius of the axle.
Inclined plane or ramp
A sloping surface on which an object can move.
IMA of an inclined plane
Length of ramp divided by height of ramp.
Screw
An inclined plane wrapped around a rod.
The tip of a screw
"The ""thread""."
Wedge
An inclined plane that travels through an object.
Mechanical System
A group of parts that interact with each other and work together to complete a task.
Efficiency
Useful work done by the machine compared to the work needed to operate.
Useful output work
Work that the machine is built to perform.
How to calculate efficiency
Useful output work over input work. Efficency is usually expressed as a percentage.
Why are Complant fluorescent lights more efficient than incandescent lights?
Because CFLs can operate at lower temperatures (30 C) , less electricity energy is converted to heat than Incandescent lights (175 C).
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