Test

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Test 3
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1. (10 points) Two boxes of mass M and 2M slide
down a ramp that is inclined 25? with the
horizontal as shown. The boxes are connected by
a string. The coefficient of kinetic friction
between the larger box and the ramp is 0.20 and
the coefficient between the smaller box and the
ramp is 0.15. What is the acceleration of the
boxes? (a) 3.1 m/s2 (b) 2.9 m/s2
(c) 2.2 m/s2 (d) 2.5 m/s2
(e) 3.4 m/s2  
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2. (10 points) A man (mass 100 kg) is
ice-skating on a frozen pond. He is moving east
with a speed of 3.0 m/s when his girlfriend who
is moving with the same speed to the north meets
him and jumps into his arms. If the direction of
the couple is then 31? north of east, what was
the mass of the girlfriend? (a) 60 kg
(b) 63 kg (c) 70 kg
(d) 55 kg (e) 58 kg  
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3. (10 points) A highway curve is banked at an
angle of ? with the horizontal. The radius of
curvature for the curve is R, the normal force
the pavement exerts on a car is N and fs is the
force of static friction on the tires of the car.
If the positive x-direction is horizontal and
the positive y-direction is vertical, which of
the following pairs of equations is correct for
the sum of the forces on a car of mass M in these
two directions if it is moving at the maximum
safe speed v for the curve?

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4. (10 points) A Ferris wheel has a diameter of
10 meters and turns at a constant speed of 6.0
rpm. What is the magnitude of the force exerted
on a 60-kg passenger by her seat when she is at
the top of the moving wheel? (a) 710 N
(b) 590 N (c) 470 N
(d) 490 N (e) 550 N  
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5. (10 points) A 3.00-kg mass attached to a 1.70
meter long string moves in a vertical circle as
shown. If the speed of the mass at a point when
it is 15? past the vertical is 5.00 m/s, what is
the tension in the string at this instant? (a)
44.1 N (b) 36.5 N (c)
22 N (d) 72.5 N (e)
15.7 N
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6. (10 points) A batter swings at a John Smoltz
fastball that is moving horizontally with a speed
of 42 m/s and pops up. The catcher catches the
ball standing on home plate at the height it was
hit 6.0 sec later. Remembering that the mass of
a baseball is 150 g, what was the magnitude of
the impulse exerted on the ball by the bat? (a)
1.8 kg?m/s (b) 7.7 kg?m/s (c) 11 kg?m/s
(d) 5.2 kg?m/s (e) 4.1 kg?m/s
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7. (5 points) A 16-ft canoe weighs 80 lbs. A
120-pound woman sits 3.0 ft from the bow and a
200-lb man sits 2.0 ft from the stern. How far
from the bow is the center of mass of the canoe
and its passengers? (a) 7.5 ft (b)
9.9 ft (c) 9.5 ft (d)
8.0 ft (e) 8.8 ft
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8. (10 points) The system shown is given a
slight nudge and it starts to move. If the
2.0-kg mass moves downwards at a constant speed,
what is the coefficient a kinetic friction ?k
between the 5.0-kg mass and the horizontal
surface? (a) 0.20 (b) 0.25
(c) 0.30 (d) 0.40
(e) 0.45
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9. (10 points) Two masses (m 3.0 kg, M 5.0 kg)
are connected by a massless rope the passes over
a massless, frictionless pulley as shown. The
inclined surface is frictionless and inclined 40?
to the horizontal. After the system is released
from rest, what the tension in the rope?  (a) 30
N (b) 36 N (c) 28 N
(d) 21 N (e) 18
N
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10. (10 points) Two masses are constrained to
move along the x-axis. A 2.0-kg mass moving at
6.0 m/s overtakes and collides with a 3.0-kg
mass moving at 3.0 m/s. After the collision
the 2.0-kg mass has a velocity of 2.4 m/s. What
is the velocity of the 3.0-kg mass after the
collision? (a) 5.4 m/s (b) 6.0
m/s (c) 3.6 m/s (d)
4.1 m/s (e) 4.6 m/s  
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11. (5 Points) Three masses are connected by a
massless rope that passes over frictionless,
massless pulleys as shown. The coefficient of
kinetic friction between the two smaller masses
and the horizontal surfaces is 0.40. The system
is released from rest and the masses begin to
move. What is the magnitude of the acceleration
of the 3.0-kg mass? (Use g10 m/s2 to simplify
calculations) (a) 2.0 m/s2 (b) 4.0
m/s2 (c) 3.8 m/s2 (d) 8.0
m/s2 (e) 6.0 m/s2