Chapter 12 Work And Energy Flashcards
Work
Transfer of energy to an body by a force and causes it to move in the direction of the force
Power
Rate in which work is done or energy is transformed
Mechanical advantage
Measures the how much a machine multiples force of distance
Joule
The unit for work
Measured as Newton’s times meters
Watt
Unit for power
Amount of power required for 1 J of work in 1 s
Simple machines
One of 6 types of machines
Basis of all other forms of machines
Compound machines
Machine made of more than one simple machine
Lever
Have a rigid arm that turns around a point where force is transferred from one part of the arm to the other
First class lever
.most common type
Example is claw hammer
Second class lever
.examples include nutcrackers, hinged doors, wheelbarrows
Third class lever
Examples are human forearm
Biceps are attached to bone near the elbow and contracts the short distance to move the hand a large distance
Pulley
Used to lift things Point in the middle of bullseye is like the middle of a lever. Rest of pulley resembles a first class lever
Block and tackle
Multiple pulleys used to put together a single unit
Wheel and axle
Made of a lever or pulley connected to a shaft
When wheel turns axle turns too.
Inclined plane
Turns a small input force into a large output force by spreading the work over a larger distance
Wedge
It pushes through wood and breaks it apart
Wedge functions like two inclined plans back to back
Screw
An inclined plan wrapped around a cylinder
Examples are jar lids, the normal screw, spiral cases
Potential energy
Energy that an object has because of its position, shape or condition
Kinetic energy
Energy of a moving object due to its motion
Mechanical energy
The amount of work an object because of that objects kinetic and potential energy
Elastic potential energy
Energy stored in any type of stretched or compressed elastic material
Example is a spring or bungee cord
Non mechanical energy
Energy that lies at the level of atoms and does not affects the motion on a large scale
Efficiency
The ratio of useful work out to work in
Expressed as a percentage
Open system
Exchange energy with space around them
Closed system
When the flow of energy in and out of a system is so small it can be ignored?
Perpetual motion machine
Theoretical machines designed to keep on going forever without any input of energy
