Work, Energy, and Power : Work, Energy, and Power
Work : Work Work is the product of the magnitude of the displacement and the component of the force acting in the direction of the displacement
Work : Work Most of the time F is in the direction of d so ? = 0° and cos 0° = 1 so…
Work is done by a force acting on a body!
Work : Work Symbol: W
Unit : J, joule
1 J = 1 Nm
If force and displacement are in the…
Same directions, + W
Opposite directions, - W
Perpendicular directions, W = 0
Work : Work Work generally falls into 2 categories:
When you force something to move against the influence of an opposing force
(push-ups & gravitational force, walking & friction, bow & elastic force)
When you change the speed of something
A net force is present
Work - graphing : Work - graphing
Work - graphing : Work - graphing
Work and Energy : Work and Energy Energy is the ability to do workOR
Work causes changes in energyOR
Work is a transfer of energy
Work and Energy : Work and Energy
Power : Power Power is the rate at which work is done or the rate at which energy is transformed.
Power : Power Symbol: P
Unit: W, Watt
1W = 1J/s
Power and Work : Power and Work Example:
One liter of gas can do a specific amount of total work. However, the POWER produced when we burn the gas can be any amount depending on the rate of burn
If…
1L is burned over 30 min or 1800 sec, like a car ~50 units of power is produced
1L is burned in 1 sec, like a supersonic jet ~90,000 units of power is produced
Energy - Types : Energy - Types Mechanical Energy: Energy due to position in a field force or energy due to movement
Non-mechanical Energy: Energy that does not fall into the above category
Energy – Flow Chart : Energy – Flow Chart
Work – Energy Principle or work done by a net force or net work done on an object : Work – Energy Principle or work done by a net force or net work done on an object
Energy Conservation : Energy Conservation The total energy is neither increased nor decreased in any process.
Energy can, however, be transformed from one type to another AND transferred from one body to another, BUT, the total amount of energy in the process remains CONSTANT!
Conservative and Nonconservative Forces : Conservative and Nonconservative Forces Conservative Force: A force such that the work done on an object by the force does not depend on the path taken, rather it depends only on the initial and final positions (gravitational, elastic, electric)
Nonconservative Force: A force such that the work done on the object by the force does depend on the path taken (friction, air resistance, rocket propulsion). A lot of times these forces generate heat or sound which are non-mechanical energies.
Work – Energy Principle Redefined : Work – Energy Principle Redefined So if energy is conserved we can write it this way using mechanical and non-mechanical energies
Work – Energy Principle & Mechanical Energy Conservation : Work – Energy Principle & Mechanical Energy Conservation If we ignore nonconservative forces (friction and the such), the implication is that no non-mechanical energies are present (heat, sound, light, etc) therefore…
Mechanical Energy Conservation : Mechanical Energy Conservation
Mechanical Energy Conservation with energy lost : Mechanical Energy Conservation with energy lost