October 12
th
October 13
th
, 2009
PHY 2048 Discussion Fall ’09
Conceptual Review: Chapter 8.59.12
A . WorkEnergy Theorem
1. Write down the workenergy theorem in two ways.
2. Only conservative forces are exerted on an object. What quantity is conserved?
3. A figure on the right shows a mass m attached to a string of negligible mass. What initial
velocity do you need to give at the lowest point for the mass to take a circular path?
4. A block with an initial velocity v slides along a track that descends
through a vertical distance h. The track is frictionless except for the
lower section; there the block slides to a stop in a distance D due to
friction. What is the change in thermal energy of the system? Does it
depend on D?
B. Center of Mass
1. Three uniform thin rods form an inverted U as shown, where L = 20 cm, M = 40g and
m = 30 g. Find the center of mass.
C. ImpulseMomentum Theorem
1. A 2kg ball drops vertically onto a floor, hitting with a speed of 20 m/s. It rebounds with an initial
speed of 10 m/s. If the ball is in contact w/ the floor for 0.05s, what is the average force exerted on the
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 Fall '08
 Field
 Physics, Center Of Mass, Energy, Force, Mass, Work, WorkEnergy Theorem, m/s, B. Center of Mass

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