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I) Multiple choice (15 questions, 5 points each)
Use the following scenario for the next two problems.
A motorcycle starts braking at t = 0, and slows down at a constant acceleration of
a = 1.2 m/s2. The motorcycle stops at t = 25 s.
1. What is the speed of the motorcycle at t = 0?
A) 15 m/s
B) 30 m/s
C) 21 m/s
D) 10 m/s
E) Not enough information is given.
2. If the speed of the motorcycle at t = 0 is doubled, what happens to the stopping distance?
Assume there is no reaction time, and the acceleration remains constant.
A) It becomes twice as long as the original stopping distance.
B) It becomes half of the original stopping distance.
C) It becomes four times as long as the original stopping distance.
D) It becomes eight times as long as the original stopping distance.
E) Not enough information is given.
Phys 114 A Winter 2015, version A
Midterm Exam 1
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Use the following scenario for the next four problems.
A ball is fired from the level ground at an initial velocity of v0. The x- and y-component
of v0 is v0x = -4.00 m/s, and v0y = 3.00 m/s, respectively, where the x-direction is defined
to be horizontally to the right, and the y-direction is defined to be vertically upward.
Ignore air resistance.
3. What is the initial speed of the ball?
A) 4.00 m/s
B) 3.00 m/s
C) 7.00 m/s
D) 5.00 m/s
E) -1.00 m/s
4. What is the initial launch angle (from the +x axis) of the ball?
A) 36.9°
B) 53.1°
C) 127°
D) 143°
E) 323°
5. What is the minimum speed of the ball during the flight?
A) 3.00 m/s
B) 4.00 m/s
C) 5.00 m/s
D) 0.00 m/s
E) Not enough information is given.
6. What is the maximum height above the ground the ball attains?
A) 0.459 m
B) 1.27 m
C) 0.917 m
D) 2.18 m
E) 0.153 m
Phys 114 A Winter 2015, version A
Midterm Exam 1
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7. You are on a train whose velocity relative to the ground is given by vtg = 30.0 m/s in the x-direction.
The x- and y-component of the velocity of you relative to the ground is given by vyg,x = 31.0 m/s and
vyg,y = 1.2 m/s, respectively. How fast are you moving relative to the train?
A) 1.0 m/s
B) 1.2 m/s
C) 1.6 m/s
D) 61 m/s
E) 31 m/s
8. An object experiences a constant acceleration of 3.00 m/s2 along the negative x-axis for 5.00 s,
attaining a velocity of v. The x- and y-component of v is vx = 12.0 m/s and vy = 16.0 m/s,
respectively. Calculate the x- and y-components of the initial velocity vector, v0, of the object.
A) v0x = 12.0 m/s and v0y = 31.0 m/s
B) v0x = 27.0 m/s and v0y = 31.0 m/s
C) v0x = -3.00 m/s and v0y = 16.0 m/s
D) v0x = -3.00 m/s and v0y = 1.00 m/s
E) v0x = 27.0 m/s and v0y = 16.0 m/s
Phys 114 A Winter 2015, version A
Midterm Exam 1
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Use the following scenario for the next two problems.
A diver runs horizontally off a diving board with an
initial speed of 2.0 m/s. The diving board is 3.2 m above
the water. The diver enters the water a horizontal
distance, d, away from the end of the diving board.
Ignore air resistance.
9. What is d?
A) 1.3 m
B) 1.6 m
C) 0.81 m
D) 0.65 m
E) 2.5 m
10. If the swimmer’s initial speed is increased by a factor of 2, how does the distance d change?
A) It will increase by a factor of 2.
B) It will increase by a factor of 4.
C) It will remain unchanged.
D) It will decrease.
E) Not enough information is given.
Phys 114 A Winter 2015, version A
Midterm Exam 1
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11. A block of mass m is placed on a rough incline. A force F is applied on the block up the incline
just enough to prevent the block from sliding down. What is the direction of the friction?
a
F
b
m
θ
d
e
c
Use the following scenario for the next two problems.
You and a boy are standing next to each other on a frictionless surface. You push him
horizontally in the positive x-direction with a constant force of 15 N for 0.050 s. The
mass of the boy is 25 kg, and your mass is 55 kg.
12. Which of the following statements best describes the motion of the boy after you stopped
pushing him?
A) He has a constant non-zero acceleration in the positive x direction.
B) He has a constant non-zero acceleration in the negative x direction.
C) He has a constant non-zero velocity in the positive x direction.
D) He has a constant non-zero velocity in the negative x direction.
E) He does not move.
13. How fast is the boy moving away from you when you stopped pushing him.
A) 0.016 m/s
B) 0.030 m/s
C) 0.044 m/s
D) 0.27 m/s
E) 0.87 m/s
Phys 114 A Winter 2015, version A
Midterm Exam 1
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Use the following scenario for the next two problems.
A 0.25-kg ball is whirled around in a vertical circular motion by a string as
shown at right. The radius of the circular path is 0.50 m. Neglect air
resistance.
14. When the ball is at the top of the circular path at position A, its speed is 3.0 m/s. What is the net
force on the ball then?
A) 4.5 N upward
B) 4.5 N downward
C) 18 N upward
D) 18 N downward
E) 2.5 N downward
15. The ball speeds up as it comes down, and slows down as it comes back up. At position B
(moving upward), which of the following the directions best represents the direction of the
acceleration of the ball?
Phys 114 A Winter 2015, version A
Midterm Exam 1
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II) Long answer (25 points)
Show all of your work to receive full credit.
Suppose Block 1 with a mass of m1 and Block 2 with a mass of m2 are on a
rough level surface. The blocks are connected by a massless string, String 1.
You are pulling another massless string, String 2, which is attached to
Block 2, causing the whole system to accelerate to the right with a constant
acceleration of a. The tensions in String 1 and String 2 are T1 and T2,
respectively. The frictional forces acting on Block 1 and Block 2 are f1 and f2,
respectively.
a.
(9 points) Draw free body diagrams of the blocks in the boxes below. Label each force
clearly, and indicate the type of each force.
Block 1
Block 2
b. (5 points) What is the coefficient of kinetic friction between Block 2 and the surface, μ2?
Give the answer in terms of f2 m2, and g (the acceleration due to gravity).
c. (5 points) What is f1 in terms of m1, T1, and a?
d. (6 points) What is f2 in terms of m2, T1, T2, and a?
Phys 114 A Winter 2015, version A
Midterm Exam 1
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