Kinetic energy

1
Kinetic energy
Consider a force F acting on an object of mass m
2
Change in K.E. work done by F
Fs
mas
? F ma
? v2 u2 2as
Change in K.E. final K.E initial K.E.
? initial K.E.
final K.E.
Simulation Work done in pulling a cargo
3
Gravitational potential energy
Consider lifting an object of mass m to a height
h above the ground
Applied force F mg
Change in P.E.
work done by F
Fh
mgh
Change in P.E. mgh
4
In which way does the cargo gain more potential
energy?
The cargo is raised by the same vertical height.
? It gains the same amount of potential energy.
5

• We should consider the change in vertical
  distance of the object
• but NOT the actual distance moved.

• A smaller force is required to push the cargo
  along the the ramp, but the distance is longer.

same amount of work done on cargo
6

• Gravitational potential energy is often measured
  with respect to a reference level.

• The potential energy at the reference level is
  taken zero.

7
Thats the end of Section 8.2
Check Point
Key Ideas
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