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Transcript PHYSICS

Gravitational Potential Energy
Can
do positive or negative work.
Example: Falling Basketball
• mg is the only force acting on the basketball.
s
• The initial height of the basketball is ho
• The final height of the ball is hf
• The displacement of the ball is s
To
mg
hO
Calculate Work
• W=(Fcos0)s with F = mg and 0 = 0°
• Wgravity = mg(ho – hf)
hf
mg
PE
= mgh
Units of GPE is joule (J)
Work
being done is equal to PE final – PE
initial.
Gravitational Potential Energy, like work
and Kinetic Energy is scalar.
Conservative
Forces:
• A force is conservative when the work it does on
a moving object is independent of the path
between the object’s initial and final positions.
• A force is conservative when it does no net work
on an object moving around a closed path,
starting and finishing at the same point.
• Work done by gravity depends only on the initial
and final heights, and not the path between
these heights.
Nonconservative:
• A forces is nonconservative if the work it does on
an object moving between two points depends
on the path of the motion between the two
points.
An
object can possess two kinds of
energy: Kinetic energy and gravitational
potential energy.
The sum of KE and PE is called total
mechanical energy.
Wnc
= (KEf-KEi) + (PEf – PEi)
The
total mechanical energy (E=KE + PE)
of an object remains constant as the
object moves, provided that the net wor
done by external nonconservative forces
is zero.
Kinetic Energy
Potential
Energy
Total
Mechanical
Energy
0J
600000 J
600000 J
200000 J
400000 J
600000 J
400000 J
200000 J
600000 J
600000 J
0J
600000 J
LAB:
Energy in Simple Harmonic
• Preliminary Questions:
Motion
Write them out and then answer.
• Procedure:
Describe what you did as detailed as possible.
• Data:
• Analysis Questions:
Write them out and then answer