p08_003.pdf

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Chapter 8 - 8.3
d ,where F is the force
and d is the displacement. The force is vertically downward and has magnitude mg ,where m is
the mass of the flake, so this reduces to W = mgh ,where h is the height from which the flake falls.
This is equal to the radius r of the bowl. Thus
·
W = mgr =(2 . 00
×
10 − 3 kg)(9 . 8m / s 2 )(22 . 0
×
10 − 2 m) = 4 . 31
×
10 − 3 J .
10 − 3 J.
(c) The potential energy when the flake is at the top is greater than when it is at the bottom by
−
W =
−
4 . 31
×
∆ U
|
If U = 0 at the bottom, then U =+4 . 31
×
10 − 3 J at the top.
10 − 3 J at the bottom.
(e) All the answers are proportional to the mass of the flake. If the mass is doubled, all answers are
doubled.
−
4 . 31
×
3. (a) The force of gravity is constant, so the work it does is given by W = F
(b) The force of gravity is conservative, so the change in gravitational potential energy of the flake-Earth
system is the negative of the work done: ∆ U =
|
.
(d) If U = 0 at the top, then U =

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