Physics 101 Practice Quiz 4

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1. A sled weighs 100 N. It is held in place on a frictionless 20° degree slope by a rope attached
to a stake at the top; the rope is parallel to the slope. What is the normal force of the slope
acting on the sled?
a. 94 N
b. 47 N
c. 37 N
d. 34 N
a
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<p>

2. Find the tension in an elevator cable if the 1 000-kg elevator is descending with an
acceleration of 1.8 m/s2, downward.
a. 5 700 N
b. 8 000 N
c. 9 800 N
d. 11 600 N
b
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<p>

3. A horizontal force of 750 N is needed to overcome the force of static friction between a level
floor and a 250-kg crate. If g = 9.8 m/s2, what is the coefficient of static friction?
a. 3.0
b. 0.15
c. 0.28
d. 0.31
d
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4. A 10.0-kg mass is placed on a 25.0o degree incline and friction keeps it from sliding. The
coefficient of static friction in this case is 0.580, and the coefficient of sliding friction is
0.520. The mass is given a shove causing it to slide down the incline. What is the frictional
force while the mass is sliding?
a. 41.4 N
b. 88.8 N
c. 46.2 N
d. 51.5 N
c
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<p>

5. Jamal pulls a 150-N sled up a 28.0° degree slope at constant speed by a force of 100 N. Near
the top of the hill he releases the sled. With what acceleration does the sled go down the hill?
a. 1.20 m/s2
b. 1.67 m/s2
c. 2.22 m/s2
d. 2.67 m/s2
d
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<p>6. A 9.0-kg hanging weight is connected by a string over a pulley to a 5.0-kg block sliding on a
flat table. If the coefficient of sliding friction is 0.20, find the tension in the string.
a. 19 N
b. 24 N

c. 32 N
d. 38 N

d
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<p>7. A thrown stone hits a window, but doesn’t break it. Instead it reverses direction and ends up
on the ground below the window. In this case, we know:
a. the force of the stone on the glass > the force of the glass on the stone.
b. the force of the stone on the glass = the force of the glass on the stone.
c. the force of the stone on the glass < the force of the glass on the stone.
d. the stone didn’t slow down as it broke the glass.
b</p>