Download PHY2053-S10 Exam II Chapters 6-10

PHY2053-S10 Exam II Chapters 6-10
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MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. Each
question is worth (5 pts)
1) A potterʹs wheel, with moment of inertia 17 kg·m 2 , is spinning freely at 40.0 rpm. The potter drops
a lump of clay onto the wheel, where it sticks a distance 1.2 m from the rotational axis. If the
subsequent angular speed of the wheel and clay is 32 rpm, what is the mass of the clay?
A) 3.3 kg
B) 3.0 kg
C) 2.6 kg
D) 2.0 kg
1)
2) At time t = 0 s, a wheel has an angular velocity of +27 rad/s. The wheel has a constant acceleration
of -0.43 rad/s2 . How long will it take to come to rest:
2)
A) 130 s
B) 150 s
C) 110 s
D) 63 s
E) 89 s
3) A child does 350 J of work while pulling a box from the ground up to his tree house with a rope.
The tree house is 8.2 m above the ground. What is the mass of the box?
A) 2.6 kg
B) 3.3 kg
C) 4.4 kg
D) 4.0 kg
3)
4) A 0.24 kg blob of clay is thrown at a wall with an initial velocity of 16 m/s. If the clay comes to a
stop in 91 x 10 -3 s, what is the average force experienced by the clay?
4)
A) 42 N
B) 35 N
C) 26 N
D) 51 N
5) The gravitational acceleration at the surface of planet X is 11.7 m/s2 , and the radius of the planet is
69,200 km. The altitude above the surface of planet X at which the weight of a body is equal to that
on the surface of the earth, in km, is closest to: ( Hint: Solve for the mass of planet X first, also note that
the altitude is what you are meant to find)
A) 10,000
B) 12,000
C) 6400
D) 9000
E) 7700
5)
PHY2053-S10 Exam II Chapters 6-10
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SHORT ANSWER. Partial credit is given even if the final answer is incorrect. So please show your work and include
any assumption you make. Also make sure your final answer includes the poper units and has the appropriate number
of significant figures. These questions are worth (15pts)
6) Two blocks of ice, one of mass 150 kg and the other of mass 600 kg are at rest on a frozen
lake. A person pushes each block the same distance d = 2.90 m. Ignore friction and assume
that a force F = 500 N is exerted on each block at an anlge of -30o to the horizontal.
a) What is the kinetic energy of the large block.
b) Find the velocity of the smaller block.
2
6)
PHY2053-S10 Exam II Chapters 6-10
Name___________________________________
Panther ID _________________________
7) A string is wrapped several times around the rim of a small hoop with a radius of R =
6.40×10−2 m and a mass of 0.380 kg. If the free end of the string is held in place and the
hoop is released from rest (see the figure ), calculate the angular speed of the rotating hoop
after it has descended 0.850 m. ( Hint use conservation of energy. The moment of inertion of a
hoop is = MR2 )
3
7)
PHY2053-S10 Exam II Chapters 6-10
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Panther ID _________________________
8) A pitcher is employing a ballistic pendulum to determine the speed of his fastball. A 4.3 kg
lump of clay is suspended from a cord 4.0 m long. When the pitcher throws his fastball
aimed at the clay, the ball becomes embedded in the clay and the two swing up to a
maximum height of 0.35 m. If the mass of the baseball is 0.21 kg, find the speed of the
pitch. ( Hint: Use conservation of momentum from 1 to 2 and conservation of energy from 2 to 3 )
4
8)
PHY2053-S10 Exam II Chapters 6-10
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Panther ID _________________________
9) In Figure 10.21, a 10.0 m long bar is attached by a frictionless hinge to a wall and held
horizontal by a rope that makes an angle θ of 39° with the bar. The bar is uniform and
weighs 54.1 N. How far from the hinge should a 10.0 kg mass be suspended for the tension
T in the rope to be 177 N?
( Hint: Frictionless means that there is no vertical component to the force at the hinge. Also use the
equilibrium condition for forces and torque to solve this problem, ie Σ F = 0 and Σ τ = 0)
5
9)
PHY2053-S10 Exam II Chapters 6-10
Name___________________________________
Panther ID _________________________
10) A Ferris wheel has radius 10.0 m and makes one revolution in 10.0 seconds. A person
weighing 890 N is sitting on one of the benches attached at the rim of the wheel.
a) What is the apparent weight of the person at the very top of her motion?
b) What is the apparent weight at the bottom
(Hint: Use free body diagrams at the top and bottom. Note that the normal force exerted on her by
the bench is the apparent weight)
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10)
Answer Key
Testname: PHY2053S10‐EXAM2‐B
1) B
2) B
3) C
4) A
5) C
6)
7)
8) 20 m/s
9) 10 meters from the hinge
10) 460 N