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OCT. 2005
Conceptual questions
1) Answer: There is only one force acting.
Comment: the force is the force of gravity, providing the centripetal acceleration to allow the
astronaut to orbit the Earth.
2) Answer: Graph is as shown:
3) Answer: Force of friction is down the plane, towards the inside of the curve.
4) Answer: The mass of the rocket is decreasing as fuel is expelled.
5) Answer: Acceleration is downwards at ‘g’ or downwards at 9.8 m/s
2
.
Comment: it’s projectile motion; acceleration is
constant
, and
always
downward at g.
Problems:
1) Patch of snow on a roof inclined at 30
o
.
a) If the snow is not sliding, then the force down the plane and the force up the plane
(friction) must balance.
F
down
= mg sin(theta)
F
friction
= μ F
N
= μ mg cos(theta)
If the two balance, then we get
μ = tan(theta) = tan(30) =
0.58
b) If the kinetic coefficient is 0.20, what is the speed of the snow at the edge of the roof?
We have the total force down the plane as:
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This note was uploaded on 04/19/2008 for the course PHYS 101 taught by Professor Prof during the Fall '08 term at McGill.
 Fall '08
 prof
 Acceleration, Force, Gravity

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