Chapter 3: Momentum & Energy Flashcards
(18 cards)
Energy
The property of matter that gives it the ability to do work
Work
What is done when matter is moved against gravity
Work=force X distance w=Fd Units = Newton*meters
(Nm) or Joules (J) 1Nm=1J
Potential Energy
Energy in a ‘stored’ state that has the potential to do work
Potential Energy= mass X gravity X height
derived from:
gravitational potential energy = weight x height
Kinetic Engergy
What’s being used when mass is moved;
Energy required to bring mass from rest to the speed it’s at OR to bring is to rest from the speed it’s at
Kinetic Energy=1/2(massXvelocity^2) KE=1/2(mv^2)
1/2 is a constant
speed= delta displacement/delta time
Conservation of Energy for Machines
The work outpout of any machine cannot exceed the work input.
Efficiency
The percentage of the work put into a machine that is convered into useful work output
Collision: Elastic
A collision in which colliding objects rebound without lasting deformation or the generation of heat
Impulse
aka ‘force time’; The product of the force acting on an object and the time during which it acts
Impulse=forceXtime
Impulse momentum relationship
Impulse is equal to the change in the momentum of an object that the impulse acts upon
Force Time = change in (momentumXvelocity)
Collision: Inelastic
A collision in which colliding objects become destorted, generate heat, and possibly stick together
Law of Conservation of Energy
Energy cannot be created nor destroyed. It can only be transformed, and the total amount of engery never changes.
Law of Conservation of Momentum
In the absence of an external force, the momentum (mass X velocity) of a system remains unchanged;
Momentum before an event involving internal forces is the same as after the event.
momentum before = momentum after
mv before = mv after
Lever
A simple machine consisting of a rigid rod pivioted at a fixed point called a fulcrum
Machine
A device, such as a lever or pylley, that increases or decreases a force or simply changes the direction of a force.
Momentum
Inertia in motion, given by the product of the mass of an object and its velocity
momentum = massXvelocity
M = mv
Power
The rate of doing work (or the rate at which energy is expended)
Rate at which energy is transformed from one form to another.
Power = work/time Unit is Watt (same as Joule/second)
Work-Energy Theorem
The net work done on an objects equals the change in kinetic engergy of the object
Work done on object = change in kinetic energy
The more kinetic energy something has, the more force is required to stop it.
Watt
Unit for power; same as one Joule/second)
