PHYS Ch. 2 Work & Energy Flashcards
What is Kinetic energy?
energy in motion
K = 1/2 mv^2; m = mass in kg, v = speed in seconds,
K = energy in J
What is the metric of Joule?
J = kg*m^2/s^2
What happens to kinetic energy when speed is doubled?
kinetic energy quadruples
What is the equation for gravitational potential energy?
U = mgh
m = mass in kg, g = 9.8m/2^2, and, h = height, U in J
What is the relationship between gravitational potential energy and mass and height?
direct proportionality; if you triple the mass, height the gravitational potential energy will triple
What happens to a spring when it is stretched from its equilibrium length?
the spring has elastic potential energy
What is the equation for elastic potential energy?
U = 1/2 kx^2
k = spring constant, x = magnitude of displacement form equilibrium
What is total mechanical energy?
the sum of an object’s kinetic and potential energy
What is the equation for total mechanical energy?
E = U + K ==> 1/2kx^2 * 1/2mv^2
What is the diff b/w conservative and nonconservative forces?
Conservative forces conserve mechanical energy and are not path-dependent. Nonconservative forces dissipate mechanical energy as thermal or chemical energy and are path-dependent; the longer the distance traveled, the larger the amount of energy that is dissipated
When is the total mechanical energy constant?
when work done by nonconservative forces is zero
What is work?
the measure of energy transfer that is heat
What is the equation for work?
W = Fd = Fd*cos (0)
F = force, d = displacement or distance traveled
What happens to the volume of a gas system when the gas expands and compresses?
when the gas expands, it pushes up against the piston, exerting a force that causes the piston to move, and the volume of the system to increase. when the gas is compressed, the piston pushes down on the gas, exerting a force that decreases the volume of the system
What happens to work when the volume of a expands and compresses?
when work is done BY a system, the gas is expanded, and the work is said to be positive. when work is done ON a system, the gas is compressed, and the work is said to be negative
What is the work done on a system when volume is constant and pressure changes?
there is no work done on the system, and there is no area to be calculated in the pressure vs. volume curve. this is an isovolumetric or isochoric process
What is the work done on a system when volume changes and pressure is constant?
if the pressure remains constant as volume changes, and the area under the curve is a rectangle in the pressure v. volume curve. this is an isobaric process, and W = P change in V
What is power?
the rate at which work is done or energy is transferred from one system to another
What is the equation for power?
P = W/t = work/time
W = change in energy
t = time
What is the unit for power?
watt (W) = J/s
What is the equation for net Work?
Wnet = change in K = Kf - Ki
K = kinetic energy
What are the 6 simple machines?
incline plane, wedge, wheel and axle, lever, pulley, and screw
What is the role of simple machines?
it allows for the same amount of work to be accomplished through a smaller applied force, providing a mechanical advantage
What are the types of potential energy?
gravitational, elastic, chemical, and electrical
Where is electrical and chemical potential energy found?
electrical potential energy exists between charged particles, and chemical potential energy is stored in bonds of compounds
What are examples of Conservative forces and Nonconservative forces?
Conservative forces are elastic, gravity, and electrostatic
Nonconservative forces are viscous drag, friction, and air resistance
What happens to work as the length of an incline plane increases?
As the length of an inclined plane increases, the amount of energy necessary to perform the same amount of work decreases
What happens to work as the effort/force of a pulley decreases?
As the effort/force decreases in a pulley system, the effort distance increases to generate the same amount of work
What is the potential energy for an object in uniform circular motion?
potential energy is constant
What happens to elastic [petinal energy when displacement is doubled?
the energy is quadrupled
What is the relationship between work done by a force, and kinetic energy?
work done by a force is proportional to the displacement of the object, and the change in kinetic energy of the object is equal to the work done by all the forces acting on the object
What is the diff b/w mechanical advantage and efficiency of a simple machine?
mechanical advantage is a ratio of the output force generated given a particular input force. efficiency is a ratio of the useful work performed BY a system compared to the work done ON a system
