Exam 1 Practice Test PDF

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PHYS 172

EXAM 1 PRACTICE (200 Points)

PROBLEM 1 (8 Points) A vehicle travels along a circular path as shown in the figure. From A to B, the vehicle maintains a constant speed of 4 m/s, from B to C, 8 m/s, and from C to D, 12 m/s. What is the average speed of the vehicle in traveling from A to D?

A) 8.0 m/s B) 6.5 m/s C) 4.0 m/s D) 3.5 m/s E) None of the above.

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PHYS 172

EXAM 1 PRACTICE (200 Points)

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PROBLEM 2-3 A small space probe of mass m= 1000 kg is launched from a space station in deep space. The space station exerts negligible gravitational force on the space probe. At time t = 0 when the initial position of the space probe (relative to the space station) is m, and it’s velocity (relative to the space station) is m/s, the space probe turns on its thrusters that exert a constant force of N. PROBLEM 2 (6 Points) Using a time step of 1 second, determine the velocity of the space probe (relative to the space station) after two time steps, i.e. at t = 2 seconds. A) m/s B) m/s C) m/s D) m/s E) None of the above PROBLEM 3 (6 Points) Using a time step of 1 second, determine the position of the space probe (relative to the space station) after two time steps, i.e. at t = 2 seconds. A) m B) m C) m D) m E) None of the above

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PROBLEM 4 (8 Points) In lab push your cart along a horizontal track and obtain the following velocity vs. time graph.

Which of the graphs below represent the position vs. time?

A)

B)

C)

D) E) None of the above

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PROBLEM 5 (8 Points) A satellite orbits the earth in a circular path at constant speed. What is the direction of the change in momentum of the satellite, as it moves from point D to point A?

A) B) C) D) E)

Direction shown by arrow labeled A in the picture on the right. Direction shown by arrow labeled B in the picture on the right. Direction shown by arrow labeled C in the picture on the right. Direction shown by arrow labeled D in the picture on the right. Direction shown by arrow labeled E in the picture on the right.

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EXAM 1 PRACTICE (200 Points)

PROBLEM 6 (8 Points) In a crash test, a car with a mass of 1500 kg is initially moving at a speed of 18 m/s just before it collides with a barrier. The final speed of the car after the collision is zero. The original length of the car is 4.48 m, but after the collision, the smashed car is only 3.86 m long. Making the very rough approximation that the large force that the barrier exerts on the car is approximately constant during contact, determine the approximate magnitude of this force? A) 2.5 x 105 N B) 7.8 x 105 N C) 1.96 x 105 N D) 3.9 x 105 N E) None of the above

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EXAM 1 PRACTICE (200 Points)

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PROBLEM 7 (8 Points) The figure below shows two negatively charged objects (with the same charge) and one positively charged object. What is the direction of the net electric force on the positively charged object? A) Horizontal to the Left B) Horizontal to the Right C) Force is zero D) There is not enough information to answer this question E) None of the above

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PROBLEM 08-09 You kicked a ball of mass 𝑚 = 2 𝑘𝑔 that was initially at rest with a force 𝐹 = 〈12, 0, −16〉 𝑁 so that the ball is now rolling on the grass field. PROBLEM 08 (6 Points) What is the initial velocity of the ball after the kick if the duration of the kick is ∆𝑡 = 0.1𝑠 𝑚 〈0.3, 0, 0.4〉 A) 𝑠

𝑚

B)

〈0.3, 0, − 0.4〉

C)

〈−0.6, 0, −0.8〉

D)

〈−0.6, 0, 0.8〉

E)

〈0.6, 0, −0.8〉 𝑠

𝑠

𝑚

𝑚 𝑠

𝑠 𝑚

PROBLEM 09 (6 Points) The net force on the rolling ball acts in the direction opposite to its momentum. Which vector below is the direction of the net force acting on the rolling ball immediately after it is kicked? 〈0.6, 0, 0.8〉 A) 〈0.6, 0, − 0.8〉 B) 〈−0.6, 0, −0.8〉 C) 〈−0.6, 0, 0.8〉 D) 〈6, 0, −8〉 E)

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EXAM 1 PRACTICE (200 Points)

PROBLEM 10 (8 Points) A ball of mass, M hangs by two strings from the ceiling as shown in the figure. The acceleration due to gravity has magnitude g, and acts vertically downward in the picture shown. What is the magnitude of the force of tension 𝑭𝑻 in each of the upper strings? A) 𝑀𝑔 B) 𝑀𝑔/2 C) 𝑀𝑔/(2 sin 𝜃) D) 𝑀𝑔/(2 cos 𝜃) E) None of the above

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PHYS 172

EXAM 1 PRACTICE (200 Points)

PROBLEM 11 (8 Points) An elevator is accelerating downward at with magnitude of acceleration a. A block of mass M hangs by a low-mass rope from the ceiling of the elevator as shown. The acceleration due to gravity has magnitude g, and acts vertically downward in the picture shown. What is the force of tension, 󰇍𝑭 𝑻 in the rope? A) 〈0, 𝑀𝑔, 0〉 B) 〈0, 𝑀𝑎, 0〉 C) 〈0, 𝑀𝑔 + 𝑀𝑎, 0〉 D) 〈0, 𝑀𝑔 − 𝑀𝑎, 0〉 E) 〈0, −𝑀𝑔 − 𝑀𝑎, 0〉

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EXAM 1 PRACTICE (200 Points)

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PROBLEM 12 (8 Points) Suppose that the period of a particular ideal mass-spring system is 4 s. What would be the period of the system if the mass were four times the original mass? A) 16 s B) 8 s C) 2 s D) 1 s E) None of the above

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PROBLEM 13 (8 Points) Three identical springs, each with stiffness 1200 N/m are attached in series (that is, end to end) to make a longer spring to hold up a heavy weight. What is the stiffness of the longer spring? A) 400 N/m B) 800 N/m C) 2400 N/m D) 3600 N/m E) None of the above

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PROBLEM 14 (8 Points)

An automobile (and its occupants) of total mass M = 2000 kg, is moving through a curved dip in the road of radius R = 20 m at a constant speed v = 20 m/s. For this analysis, you can neglect air resistance. Consider the automobile (and its occupants) as the system of interest. Use g = 10 m/s2. Calculate the magnitude of the normal force exerted by the road on the system (car and its occupants). A) B) C) D) E)

20,000 N 40,000 N 60,000 N 30,000 N 50,000 N

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EXAM 1 PRACTICE (200 Points)

PROBLEM 15 (8 Points) A piece of cork (density 250 kg/m3) of mass 0.01 kg is held in place under water (density 1000 kg/m3) by a string. What is the tension, T, in the string? [Use g = 10 m/s2] A) 0.1 N B) 0.2 N C) 0.3 N D) 0.4 N E) 0.5 N

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EXAM 1 PRACTICE (200 Points)

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PROBLEM 16 (8 Points) A thin platinum bar is 1 m long with a 1 mm X 1 mm cross section and is attached to the ceiling. When a 10 kg mass hangs from the bar it stretches 2.0 mm. If we hang the same 10 kg mass from a 2 m long platinum bar that has a 2 mm X 2 mm cross section, how much will that bar stretch? A)

0.5 mm

B)

1.0 mm

C)

2.0 mm

D)

4.0 mm

E)

None of the above

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EXAM 1 PRACTICE (200 Points)

PROBLEM 17 (8 Points) Two boxes move together with the same acceleration across an icy surface as you push with a horizontal force of magnitude F, as shown below. The mass of box 1 is 60 kg, and the mass of box 2 is 20 kg. What is the best estimate of the magnitude of the net force acting on box 1? A) F/4 B) F C) 3F/4 D) F/2 E) F/3

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EXAM 1 PRACTICE (200 Points)

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PROBLEM 18 (8 Points) A crate of mass 100 kg sits on a horizontal floor. The coefficient of static friction between the crate and the floor is 0.60, and the coefficient of kinetic friction is 0.50. What is the magnitude of the frictional force on the crate if you push it with horizontal force of 400N? What is the magnitude of the frictional force on the crate if you push it with a horizontal force of 700N? [Use g = 10 m/s2] A) 600 N when you push it with a force of 400 N 500 N when you push it with a force of 700 N B) 400 N when you push it with a force of 400 N 500 N when you push it with a force of 700 N C) 600 N in both cases. D) 500 N in both cases E) None of the above

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EXAM 1 PRACTICE (200 Points)

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PROBLEM 19 (8 Points) A small sports car with a mass of 1000 kg accelerates in a straight line from rest to 30 m/s (more than 60 miles/hour) in 4s. What is the magnitude of the average force causing the change in the car’s momentum during these 4 seconds, and what causes this force? A) 30,000 N caused mainly by the force exerted by the road on the car’s tires B) 30,000 N caused mainly by the force exerted by car’s tires on the road C) 7500 N caused mainly by the force exerted by the road on the car’s tires D) 7500 N caused mainly by the force exerted by car’s tires on the road E) 7500 N caused mainly by the force exerted by exploding gasoline on the cylinders of the car’s engine

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EXAM 1 PRACTICE (200 Points)

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PROBLEM 20 (8 Points) A 1000 kg sedan traveling north at a velocity of m/s, collides at an intersection with a 3000 kg minivan traveling west with a velocity of m/s. What is the final velocity of the wreckage of the two of them stuck together just after the collision? A) m/s B) m/s C) m/s D) m/s E) None of the above

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EXAM 1 PRACTICE (200 Points)

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PROBLEM 21-24 A block of mass m is attached by a spring with stiffness 𝑘𝑠 to a wall at the top of a slippery ramp as shown in the figure. The spring’s relaxed length is 𝐿𝑜 . At time 𝑡 = 0 the spring’s stretched length is 𝐿 and the block’s velocity is 𝑣𝑖 .

PROBLEM 21 (6 Points) Which of the following is an accurate free body diagram representing the forces acting on the block?

A) Diagram A B) Diagram B C) Diagram C D) Diagram D E) None of the above

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For the next three problems, use the diagram shown above. The mass of the block is 𝑚 = 5 𝑘𝑔, the angle of the incline plane 𝜃 = 30°. The spring stiffness is 𝑘𝑠 = 50 𝑁/𝑚. The relaxed length of the spring is 𝐿0 = 0.5 𝑚. The origin of the coordinate system shown is at the top of the incline plane, such that the initial position of the block is 𝑟𝑖 = 〈−𝐿, 0,0〉 = 〈−0.60,0,0〉 𝑚, and its initial velocity is 𝑣𝑖 = 〈−1,0,0〉 𝑚/𝑠. Use g = 10 m/s2. PROBLEM 22 (6 Points) What is the net force acting on the block? A) 〈−20, 0,0 〉𝑁 B) 〈−25, 0,0 〉𝑁 C) 〈5, 0,0 〉𝑁 D) 〈−30, 0,0 〉𝑁 E) None of the above

PROBLEM 23 (6 Points) What is the momentum of the block in the time interval of 0.1 seconds? A) 〈−2, 0,0 〉 𝐾𝑔 𝑚/𝑠 B) 〈−3, 0,0 〉 𝐾𝑔 𝑚/𝑠 C) 〈−5, 0,0 〉 𝐾𝑔 𝑚/𝑠 D) 〈−7, 0,0 〉 𝐾𝑔 𝑚/𝑠 E) None of the above

PROBLEM 24 (6 Points) What is the position of the block at the end of this time interval of 0.1 seconds? A) 〈−0.14, 0,0 〉 𝑚 B) 〈−0.60, 0,0 〉 𝑚 C) 〈−0.64, 0,0 〉 𝑚 D) 〈−0.74, 0,0 〉 𝑚 E) None of the above

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EXAM 1 PRACTICE (200 Points)

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PROBLEM 25-28 Both boxes are initially at rest on horizontal ice (frictionless). You apply a force as shown on the top block, such that the two blocks move together.

PROBLEM 25 (6 Points) Which of the following is the correct free body diagram for the system comprising both blocks?

A) Diagram A B) Diagram B C) Diagram C D) Diagram D E) None of the above

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PROBLEM 26 (6 Points) What is the magnitude of the acceleration of the system of two blocks moving together?

A) B) C) D) E)

1 𝑚1 +𝑚2 1 𝑚2 1 𝑚1

𝐹

𝐹 𝐹 1

𝑚2 −𝑚1

𝐹

None of the above

PROBLEM 27 (6 Points) Which of the following is the correct free body diagram for the system comprising ONLY the bottom block?

A) Diagram A B) Diagram B C) Diagram C D) Diagram D E) None of the above

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EXAM 1 PRACTICE (200 Points)

PROBLEM 28 (6 Points) What is the magnitude of the force on bottom block due to the top block?

A) B) C) D) E)

𝑚1 𝑚1 +𝑚2 𝑚1 𝑚2

𝐹

𝑚2 𝑚1 +𝑚2 𝑚2 𝑚2

𝐹

𝐹

𝐹

None of the above

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