Work and Energy Lecture Notes

Flashcards based on the key concepts from the 'Work and Energy' lecture notes.

The amount of _ by a steady force is the amount of _ multiplied by the _ an object moves parallel to that force.

Work

Work is measured in units of , abbreviated __.

Joules (J)

_ work is done by a force _ to an object’s displacement.

Positive

_ work is done by a force ___ to an object’s displacement.

Negative

Work is a _ – it can be positive or negative, but does not have _.

Scalar; direction

The area under a is work.

Force vs. displacement graph

All forms of energy have units of __, abbreviated __.

Joules (J)

Kinetic energy: . Here, m is the _ of the object, and v is its __.

KE = 1/2 mv^2; mass; velocity

Gravitational potential energy: . Here, m is the of the object, g is the , and h is the of the object above the _.

PE = mgh; mass; acceleration due to gravity; height; reference level

Spring potential energy: . Here, k is the __, and x is the __ the spring is stretched or compressed from its equilibrium position.

PE_spring = 1/2 kx^2; spring constant; distance

The term ___ refers to the sum of a system’s __.

Mechanical energy; potential and kinetic energies

Rotational kinetic energy: KErot = ½Iω^2. Here, I is the of the object, and ω is the __ of the object.

Moment of inertia; angular velocity

___ is heat energy that causes an increase in the ___ of the system.

Thermal energy; temperature

Before starting a work-energy problem, define the ___, and the two __ being described.

system; positions

The states…. Sum of all energy forms in position 1 + work done by external forces = sum of all energy in position 2.

Work-energy theorem

If you choose the system such that there is no external force doing work, then the system’s mechanical energy is __.

conserved

is when the total mechanical energy before some event is ___ to the total mechanical energy after the event.

Conservation of mechanical energy; equal

The remains constant throughout the motion.

mechanical energy

When dealing with an object _ from a spring, it’s easiest to consider the _.

released; spring force

The __ of the spring-earth-object system is _, where x is measured from the position where the object would hang in equilibrium.

Potential energy; 1/2kx^2

You get to ignore the _.

effects of damping or friction

is defined as the amount of in one second, or in one second: power = work / time.

Power; work; energy transfer

The units of power are , which are also written as ___..

Watts (W); Joules/second

An of calculating power when a constant force acts is _.

alternative method; average power = (force x distance) / time