F N A) 330 N 0.31 B) 310 N 0.33 C) 250 N 0.27 D) 290 N 0.30 E) 370 N 0.26

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1 Physics 23 Exam 2 Spring 2010 Dr. Alward Page 1 1. A 250-N force is directed horizontally as shown to push a 29-kg box up an inclined plane at a constant speed. Determine the magnitude of the normal force, F N, and the coefficient of kinetic friction, µ k. F N µ k A) 330 N 0.31 B) 310 N 0.33 C) 250 N 0.27 D) 290 N 0.30 E) 370 N A 4-kg block is connected by means of a massless rope to a 2-kg block as shown in the figure. Complete the following statement: If the 4-kg block is to begin sliding, the coefficient of static friction between the 4-kg block and the surface must be A) less than zero. B) greater than 2. C) greater than 1, but less than 2. D) greater than 0.5, but less than 1. E) less than 0.5, but greater than zero. Page 1

A 4-kg block is connected by means of a massless rope to a 2-kg block as shown in the figure.

2 Physics 23 Exam 2 Spring 2010 Dr. Alward Page 2 3. A block of mass M is hung by ropes as shown. The system is in equilibrium. The point O represents the knot, the junction of the three ropes. Which of the following statements is true concerning the magnitudes of the three forces in equilibrium? A) F1 F2 F3 B) F2 2F3 C) F2 F3 D) F3 F1 F2 2 F F E) 1 3 Use the following to answer question 4: A rope holds a 10-kg rock at rest on a frictionless inclined plane as shown. 4. Determine the tension in the rope. A) 9.8 N B) 20 N C) 49 N D) 85 N E) 98 N Page 2

Which of the following statements is true concerning the magnitudes of the three forces in equilibrium?

3 Physics 23 Exam 2 Spring 2010 Dr. Alward Page 3 5. The second hand on a watch has a length of 4.50 mm and makes one revolution in s. What is the speed of the end of the second hand as it moves in uniform circular motion? A) m/s B) m/s C) m/s D) m/s E) m/s 6. A car traveling at 20 m/s follows a curve in the road so that its centripetal acceleration is 5 m/s 2. What is the radius of the curve? A) 4 m B) 8 m C) 80 m D) 160 m E) 640 m 7. In an amusement park ride, a child stands against the wall of a cylindrical room that is then made to rotate. The floor drops downward and the child remains pinned against the wall. If the radius of the room is 2.15 m and the relevant coefficient of friction between the child and the wall is 0.600, with what minimum speed is the child moving if he is to remain pinned against the wall? A) 7.26 m/s B) 3.93 m/s C) 12.1 m/s D) 5.93 m/s E) 9.80 m/s 8. The Earth exerts the necessary centripetal force on an orbiting satellite to keep it moving in a circle at constant speed. Which one of the following statements best explains why the speed of the satellite does not change although there is a net force exerted on it? A) The satellite is in equilibrium. B) The acceleration of the satellite is zero m/s 2. C) The centripetal force has magnitude mv 2 /r. D) The centripetal force is canceled by the reaction force. E) The centripetal force is always perpendicular to the velocity. Page 3

A car traveling at 20 m/s follows a curve in the road so that its centripetal acceleration is 5 m/s 2. What is the radius of the curve? A) 4 m B) 8 m C) 80 m D) 160 m E) 640 m 7.

4 Physics 23 Exam 2 Spring 2010 Dr. Alward Page 4 9. A satellite is placed in equatorial orbit above Mars, which has a radius of 3397 km and a mass M M = kg. The mission of the satellite is to observe the Martian climate from an altitude of 488 km. What is the orbital period of the satellite? A) s B) s C) s D) s E) s 10. Jupiter has a mass that is roughly 320 times that of the Earth and a radius equal to 11 times that of the Earth. What is the acceleration due to gravity on the surface of Jupiter? A) 2.7 m/s 2 B) 9.8 m/s 2 C) 26 m/s 2 D) 87 m/s 2 E) 260 m/s 2 Use the following to answer question 11: A rope holds a 10-kg rock at rest on a frictionless inclined plane as shown. 11. Determine the magnitude of the acceleration of the rock down the inclined plane if the rope breaks. A) zero m/s 2 B) 4.9 m/s 2 C) 5.7 m/s 2 D) 8.5 m/s 2 E) 9.8 m/s 2 Page 4

08 10 5 s E) 7.27 10 12 s 10. Jupiter has a mass that is roughly 320 times that of the Earth and a radius equal to 11 times that of the Earth.

5 Physics 23 Exam 2 Spring 2010 Dr. Alward Page The wheels of an automobile are locked as it slides to a stop from an initial speed of 30.0 m/s. If the coefficient of kinetic friction is and the road is horizontal, approximately how long does it take the car to stop? A) 4.22 s B) 5.10 s C) 8.75 s D) 10.4 s E) 15.3 s 13. Use the work-energy theorem to find the force required to accelerate an electron (m = kg) moving along the x axis from m/s to m/s in a distance of m. A) N B) N C) N D) N E) N 14. A woman stands on the edge of a cliff and throws a stone vertically downward with an initial speed of 10 m/s. The instant before the stone hits the ground below, it has 450 J of kinetic energy. If she were to throw the stone horizontally outward from the cliff with the same initial speed of 10 m/s, how much kinetic energy would it have just before it hits the ground? A) 50 J B) 100 J C) 450 J D) 800 J E) 950 J 15. A projectile is launched with a momentum of 200 kg m/s and 1000 J of kinetic energy. What is the mass of the projectile? A) 5 kg B) 10 kg C) 20 kg D) 40 kg E) 50 kg Page 5

Use the work-energy theorem to find the force required to accelerate an electron (m = 9.11 10 31 kg) moving along the x axis from 4.00 10 6 m/s to 1.60 10 7 m/s in a distance of 0.0125 m. A) 8.

6 Physics 23 Exam 2 Spring 2010 Dr. Alward Page A bat strikes a kg baseball so that its velocity changes by +32 m/s in s. With what average force was the ball struck? A) +20 N B) 20 N C) +200 N D) 200 N E) +10 N 17. Two objects of equal mass collide on a horizontal frictionless surface. Before the collision, object A is at rest while object B has a constant velocity of 12 m/s. After the collision, the two objects are stuck together. What is the speed of the composite body (A + B) after the collision? A) 3.0 m/s B) 6.0 m/s C) 12 m/s D) 24 m/s E) 36 m/s 18. A 0.50-kg bomb is sliding along an icy pond (frictionless surface) with a velocity of 2.0 m/s to the west. The bomb explodes into two pieces. After the explosion, a 0.20-kg piece moves south at 4.0 m/s. What are the components of the velocity of the 0.30-kg piece? A) 4.0 m/s north, 0 m/s B) 2.7 m/s north, 3.3 m/s west C) 4.0 m/s north, 2.7 m/s west D) 0 m/s, 2.0 m/s east E) 4.0 m/s north, 2.0 m/s east 19. A roller coaster starts from rest at the top of an 18-m hill as shown. The car travels to the bottom of the hill and continues up the next hill that is 10.0 m high. How fast is the car moving at the top of the 10.0-m hill, if friction is ignored? A) 6.4 m/s B) 8.1 m/s C) 13 m/s D) 18 m/s E) 27 m/s Page 6

Before the collision, object A is at rest while object B has a constant velocity of 12 m/s. After the collision, the two objects are stuck together.

7 Physics 23 Exam 2 Spring 2010 Dr. Alward Page A physics student shoves a 0.50-kg block from the bottom of a frictionless 30.0 inclined plane. The student performs 4.0 J of work and the block slides a distance s along the incline before it stops. Determine the value of s. A) 8.0 cm B) 16 cm C) 82 cm D) 160 cm E) 330 cm Page 7

Physics 125 Practice Exam #3 Chapters 6-7 Professor Siegel

Physics 125 Practice Exam #3 Chapters 6-7 Professor Siegel Name: Lab Day: 1. A concrete block is pulled 7.0 m across a frictionless surface by means of a rope. The tension in the rope is 40 N; and the