chapter 9 Flashcards
potential energy is associated with…
position
kinetic energy is associated with….
motion
what is energy measured in
Joules
What is Work
a process that changes the energy of a system by mechanical means, pushing or pulling
what’s the energy principle
energy cannot be created or destroyed,
What is power
the rate at which energy is transferred or transformed
symbol for kinetic energy
K
Symbol for potential energy
U
whats the environement
objects external to the system but exerting forces on the system
whats the system
objects whose motion and environment we wish to analyze
law of conservation of energy
As long as the system is not interacting with the environment, the total energy of the system is unchanged.
interactions with environment
can transfer energy in and out of the system
Two ways to transfer energy
through work (pushing or pulling using forces) or thermal means
energy principle formula
(triangle)Esys= Wext
energy is transformed within the system without
loss
energy is transferred to and from the system by
forces of the environment
The energy of an isolated system—one that doesn’t interact with its environment—does not change. We say it is
conserved
draw a before and after representation of a particle of mass m acted on by a constant force acting parrallel
nice pic
kinetic energy equation
K=1/2mv^2
if kinetic energy is negative the particle….and if its positive….
slows down, speeds up
all forms of energy are measured in
Joules (J)
whats the kinetic energy of a .5kg mass moving at 4m/s
4J
A 1000 kg car has a speed of 20 m/s. A 2000 kg truck has a speed of 10 m/s. Which has more kinetic energy?
the car
tell me every part of this equation: (triangle)K=Kf-Ki=W
change is sutems kinetic energy=final kinetic energy - inital kinetic energy (aka amount of work done by external force)
A 5.0 kg cannonball is fired straight up at 35 m/s. What is its speed after rising 45 m?
18m/s
If the force causes the particle to speed up, then the work done by that force is
positive
negative work means that the force is causing the object to
slow and lose energy
work is positive when the force acts in the direction of the
displacement
work is negative when force and displacement are
in opposite directions
When work = 0, the particle
does’nt move
A rock falls to the bottom of a deep canyon. Is the work done on the rock by gravity positive, negative, or zero
positive, displacement and gravity both downwards
A force perpendicular to the displacement does
no work
Two equal-mass pucks on frictionless ice are pushed toward each other by two equal but opposite forces. Is the total work positive, negative, or zero?
zero
