PHYS Ch. 2 Work & Energy

Question 1

What is Kinetic energy?

Answer 1

energy in motion
K = 1/2 mv^2; m = mass in kg, v = speed in seconds,
K = energy in J

Question 2

What is the metric of Joule?

Answer 2

J = kg*m^2/s^2

Question 3

What happens to kinetic energy when speed is doubled?

Answer 3

kinetic energy quadruples

Question 4

What is the equation for gravitational potential energy?

Answer 4

U = mgh
m = mass in kg, g = 9.8m/2^2, and, h = height, U in J

Question 5

What is the relationship between gravitational potential energy and mass and height?

Answer 5

direct proportionality; if you triple the mass, height the gravitational potential energy will triple

Question 6

What happens to a spring when it is stretched from its equilibrium length?

Answer 6

the spring has elastic potential energy

Question 7

What is the equation for elastic potential energy?

Answer 7

U = 1/2 kx^2
k = spring constant, x = magnitude of displacement form equilibrium

Question 8

What is total mechanical energy?

Answer 8

the sum of an object’s kinetic and potential energy

Question 9

What is the equation for total mechanical energy?

Answer 9

E = U + K ==> 1/2kx^2 * 1/2mv^2

Question 10

What is the diff b/w conservative and nonconservative forces?

Answer 10

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

Question 11

When is the total mechanical energy constant?

Answer 11

when work done by nonconservative forces is zero

Question 12

What is work?

Answer 12

the measure of energy transfer that is heat

Question 13

What is the equation for work?

Answer 13

W = Fd = Fd*cos (0)
F = force, d = displacement or distance traveled

Question 14

What happens to the volume of a gas system when the gas expands and compresses?

Answer 14

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

Question 15

What happens to work when the volume of a expands and compresses?

Answer 15

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

Question 16

What is the work done on a system when volume is constant and pressure changes?

Answer 16

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

Question 17

What is the work done on a system when volume changes and pressure is constant?

Answer 17

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

Question 17

What is power?

Answer 17

the rate at which work is done or energy is transferred from one system to another

Question 18

What is the equation for power?

Answer 18

P = W/t = work/time
W = change in energy
t = time

Question 19

What is the unit for power?

Answer 19

watt (W) = J/s

Question 20

What is the equation for net Work?

Answer 20

Wnet = change in K = Kf - Ki
K = kinetic energy

Question 21

What are the 6 simple machines?

Answer 21

incline plane, wedge, wheel and axle, lever, pulley, and screw

Question 22

What is the role of simple machines?

Answer 22

it allows for the same amount of work to be accomplished through a smaller applied force, providing a mechanical advantage

Question 23

What are the types of potential energy?

Answer 23

gravitational, elastic, chemical, and electrical

Question 24

Where is electrical and chemical potential energy found?

Answer 24

electrical potential energy exists between charged particles, and chemical potential energy is stored in bonds of compounds

Question 25

What are examples of Conservative forces and Nonconservative forces?

Answer 25

Conservative forces are elastic, gravity, and electrostatic
Nonconservative forces are viscous drag, friction, and air resistance

Question 26

What happens to work as the length of an incline plane increases?

Answer 26

As the length of an inclined plane increases, the amount of energy necessary to perform the same amount of work decreases

Question 27

What happens to work as the effort/force of a pulley decreases?

Answer 27

As the effort/force decreases in a pulley system, the effort distance increases to generate the same amount of work

Question 28

What is the potential energy for an object in uniform circular motion?

Answer 28

potential energy is constant

Question 29

What happens to elastic [petinal energy when displacement is doubled?

Answer 29

the energy is quadrupled

Question 30

What is the relationship between work done by a force, and kinetic energy?

Answer 30

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

Question 31

What is the diff b/w mechanical advantage and efficiency of a simple machine?

Answer 31

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