Phys151_PPLNine.F12[1]

# Now work f d 200 1 200 joules if i pushed the

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Now Work = F . d = 200 . 1 = 200 Joules If I pushed the suitcase up a 5- m ramp rather than lift it up directly, what work did I do?

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“Ramping it Up” The answer is still 200 Joules! But we arrive at this answer in a different way. Because of the ramp, the force applied - remember how a sloping track reduces the effect of the Earth’s gravity! - is reduced by a factor of 1/5, the slope of the ramp. However, the distance of action of the force is increased by 5/1. These two factors negate each other in the computation of work. But using the ramp makes the work easier! Work = LARGE FORCE . small distance ([20.10].1) = small force . LARGE DISTANCE ([20.10.1/5].5) 5 1 W W.1/5
Work and Energy Work : the process of making things happen. Tied to another important concept in Physics. This is Energy : the capacity to make things happen. When you do work, you say you sap your energy - so what is the connection between work and energy in Physics? Work reduces your energy while “being worked on” raises it. I lift a suitcase. I have done work on it. I drop the suitcase on my foot. Ouch, the suitcase has done work (damage) on my foot! The suitcase in the lifted position has the capacity to do work. We say it has energy which I gave to it. Because this “stored work” is tied to the position of the suitcase (how high it is), we call it potential energy.

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Gravitas! Energy possessed by virtue of the location or state of an object is called its potential energy . A stretched rubber band can do work. It has elastic potential energy . When the location is an object’s height above some other point/level and the object got to that position because work was performed against the pull of gravity, the potential energy is called gravitational potential energy, GPE .
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• Spring '09
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