Work and Energy

Question 1

Energy

Answer 1

systems ability to do work

Question 2

Kinetic Energy

Answer 2

energy of motion

KE = 1/2 mv^2

v is NOT velocity, its SPEED

not dependent on velocity vector

Question 3

Joule

Answer 3

unit of energy

1J = 1 kg m^2 / s^2

Question 4

Potential Energy

Answer 4

energy associated given an objects position in space

potential to do work

ex: chemical/electrical

2 Types for Movement: Gravitational and Elastic

Question 5

Gravitational Potential Energy

Answer 5

depends on an objects position with respect to datum

U = mgh

Question 6

Datum

Answer 6

level identified as ground or the zero potential energy position

Question 7

Elastic Potential Energy

Answer 7

springs and other elastic systems

when a spring is stretched or compressed from its equilibrium length, the spring has elastic potential energy

U = 1/2 k x^2

x = magnitude of displacement

k = spring constant

Question 8

Total Mechanical Energy

Answer 8

summation of an objects potential and kinetic energies

E = U + K

Question 9

First Law of Thermodynamics

Answer 9

accounts for conservation of mechanical energy, meaning energy is neither created nor destroyed

NOT ALWAYS CONSTANT as other forms of energy not always accounted (thermal from friction)

Question 10

Conservative Forces

Answer 10

path independent and do not dissipate energy

have potential energy associated with them

gravitational/electrical

Question 11

Methods of Determining Conservative Forces

Answer 11

1) object moves and comes back to its starting point with a net change of 0 for energy
2) other method is when an object goes from one point to another, the energy change is equivalent regardless of the path taken

Question 12

Nonconservative Forces

Answer 12

friction, air resistance, viscous drag

path dependent

W = delta E = deltaU + deltaK

work done by nonconservative forces will be exactly the amount of energy lost from system

Question 13

Work

Answer 13

process of how energy is transferred

W = Fd = Fdcos(theta)

F and d are magnitude of force and distance

only forces parallel or antiparallel to the displacement vector will do work

Question 14

Piston

Answer 14

as gas expands, it pushes up on piston exerting a force to cause it to go up and increase the volume of the system

when gas is compressed, the piston pushes down on the gas, exerting a force to decrease volume of the system

Work is done when the volume of the system changes due to an applied pressure

Question 15

PV Curve

Answer 15

Pressure is Y, Volume is X

work done can be determined by finding the area under the curve

Question 16

As gas expands, work done is _____ and when a gas is compressed, work done is ____.

If volume stays constant as pressure changes, then ___ work is done, This is an _______ process.

If pressure remains constant and the volume changes, then the area under curve (work) is

W = P deltaV.

This is a _______ process

Answer 16

positive, negative

zero

isochoric/isovolumetric

isobaric

Question 17

Power (watts)

Answer 17

rate at which energy is transfered from one system to another

P = W/t = delta E / t

W = work

Question 18

Work Energy Theorem

Answer 18

direct relationship between the work done by all forces acting on an object and the change in kinetic energy of that object

Wnet = deltaK = Kf - Ki

Question 19

Mechanical advantage

Answer 19

any device that allows work to be accomplished through a smaller applied force

ratio of magnitude of force exerted ON an object BY a simple machine to the force actually applied ON the simple machine

Fout / Fin

Question 20

Simple machines

Answer 20

increase mechanical advantage

wedge, wheel and axle, lever, pulley, screw

Question 21

Efficiency

Answer 21

Efficiency = Wout/Win = (load)(load distance) / (effort)(effort distance)