Copyright © Michael Richmond.
This work is licensed under a Creative Commons License.
Non-conservative forces and Power
- The work done by a non-conservative force
does depend upon the path taken. Friction, for example,
does less work on a book dragged across a table if the
book is dragged straight across than if the book
is dragged in a curved path.
- The conservation laws obeyed by conservative forces
(such as gravity) are broken by non-conservative forces.
For example, the equation of conservation of Mechanical Energy
KE(final) + GPE(final) = KE(initial) + GPE(initial)
becomes
KE(final) + GPE(final) = KE(initial) + GPE(initial) + W(nc)
where W(nc) is the work done by non-conservative forces.
- Power is the rate at which work is done, or energy is spent:
work (Joules)
Power = ------ -------- = Watts
time (second)
One watt is a tiny amount of power; ordinary light bulbs produce
60 or 100 Watts.
Viewgraphs
Answer to the puzzle of the block-and-plank clock:
Copyright © Michael Richmond.
This work is licensed under a Creative Commons License.