Seat # Physics P201 D. Baxter/R. Heinz EXAM #1 September 26, 2002 7:00 9:00 PM INSTRUCTIONS 1. Sit in SEAT # given above. 2. DO NOT OPEN THE EXAM UNTIL YOU ARE TOLD TO DO SO. 3. Print your name (last name first) and blacken in the letters on the answer sheet with a #2 pencil. 4. Print your student number (identification number) and blacken in the numbers on the answer sheet with a #2 pencil. 5. Use the fronts and backs of the question sheets for scratch work. Do not use any other scratch sheets. 6. This is a multiple choice exam. Blacken in the answer to each question on the answer sheet. Fill in one and only one answer to each question. 7. Keep your eyes on your own work. 8. You have two hours to complete the exam. When you finish, please show your picture ID as you turn in your answer sheet. Please leave quietly so others are not disturbed. 9. THERE ARE 24 QUESTIONS PLEASE ANSWER ALL OF THEM. THERE IS NO PENALTY FOR GUESSING! This is a closed book, closed note exam! You may use only a calculator and one self-prepared sheet of formulas.
1. Two forces, one with a magnitude of 3 N and the other with a magnitude of 5 N, are applied to an object. For which orientation of the forces is the magnitude of the acceleration of the object the least? a. I b. II c. III d. IV e. V 2. A crate rests on a horizontal surface and a woman pulls on it with a 10-N force. Rank the situations shown below according to the magnitude of the normal force exerted by the surface on the crate, least to greatest. a. 3, 1, 2 b. 2, 1, 3 c. 2, 3, 1 d. 1, 3, 2 e. 3, 2, 1
3. A box with a weight of 50 N rests on a horizontal surface. A person pulls horizontally on it with a force of 10 N and it does not move. To start it moving, a second person pulls vertically upward on the box. If the coefficient of static friction is 0.4, what is the smallest vertical force for which the box moves? a. 5 N b. 10 N c. 15 N d. 25 N e. 35 N 4. Two ropes are attached to a 20 kg object in outer space. The first rope applies a force of 30 N and the second, 40 N. These are the only two forces acting on the object. If the two ropes are perpendicular to each other, what is the magnitude of the resultant acceleration of the object? a. 1.0 m/s 2 b. 1.5 m/s 2 c. 2.0 m/s 2 d. 2.5 m/s 2 e. 3.0 m/s 2 5. The net force on a moving object suddenly becomes zero. The object then: a. stops abruptly b. stops during a short time interval c. changes direction d. continues at constant velocity e. slows down gradually 6. Doug hits a hockey puck, giving it an initial velocity of 6.0 m/s. If the coefficient of kinetic friction between ice and puck is 0.050, how far will the puck slide before stopping? a. 27 m b. 37 m c. 47 m d. 57 m e. 67 m
7. A baseball batter hits an incoming 40 m/s fastball. The ball leaves the bat at 50 m/s after a ball-on-bat contact time of 0.030 s. What is the average force exerted on the 0.15 kg baseball during contact? a. 450 N b. 250 N c. 150 N d. 90 N e. 50 N 8. The coefficient of static friction between the tires of a car and the street is µ s = 0.76. Of the following, what is the steepest inclination angle of a street on which a car can be parked (with wheels locked) without slipping? a. 22.5 b. 37 c. 60 d. 45 e. 30 9. A bee flies to a flower 600 m due south of its hive. The bee s speed in still air is 0.75 m/s, and there is a wind blowing toward the south at 0.25 m/s. How long will it take the bee to travel to the flower and back to the hive? a. 28 min b. 30 min c. 32 min d. 34 min e. 36 min 10. The horizontal surface on which three masses slide is frictionless. If M = 3.0kg and the force F = 30 N, what is the tension on string 1 (between the two equal masses)? a. 12 N b. 15 N c. 18 N d. 24 N e. 30 N
11. An airplane of mass 1.2 10 4 kg tows a glider of mass 0.6 10 4 kg. The airplane propellers provide a net forward thrust of 3.6 10 4 N. What is the glider s acceleration? a. 2.0 m/s 2 b. 3.0 m/s 2 c. 6.0 m/s 2 d. 9.8 m/s 2 e. 12 m/s 2 12. A block slides down a frictionless ramp with an acceleration whose magnitude is 3.57 m/s 2. If it starts from rest and the ramp is 4.10 m long, how fast is it moving when it reaches the bottom of the ramp? a. 1.72 m/s b. 2.59 m/s c. 3.57 m/s d. 4.26 m/s e. 5.41 m/s 13. A ball is thrown into the air at an angle of 45 with respect to the horizontal follows a parabolic trajectory. At the highest point in the trajectory a. The velocity is zero, but the acceleration is not zero. b. Both the velocity and the acceleration are zero. c. The acceleration is zero, but the velocity is not zero. d. The ball is at rest. e. Neither the acceleration nor the velocity is zero. 14. A boy plans to paddle a rubber raft across a river to the east bank while the current flows down river from north to south at 1.0 m/s. In what direction should he head to get across the river to any spot on the opposite bank in the least amount of time if he is able to paddle the raft at 1.5 m/s in still water? a. Directly to the east b. 20 south of east c. 20 north of east d. 30 north of east e. all four directions require the same time to cross the river.
15. A 16 lb fish is weighed with two spring scales, each of negligible weight, as shown here. Which statement is true? a. Each scale will read 8 lbs. b. Each scale will read 16 lbs. c. The top scale will read 16 lbs, and the bottom one will read zero. d. The bottom scale will read 16 lbs, and the top one will read zero. e. Each scale may show a different reading, but the sum of the two readings will be 16 lbs. 16. An object is thrown vertically up into the air. Which of the following five graphs represents y component of the velocity (v) of the object as a function of the time (t)? (Take the positive y axis to be directed upwards.) a. I b. II c. III d. IV e. V
17. In this class we generally neglect air resistance but one can compute the size of the force on an object due to such resistance under some circumstances. One formula for such a force (called the drag force) is: 2 Fdrag = Cρv A where A is an area, ρ is a mass density (kg/m 3 ) and v is a speed (magnitude of velocity). If all quantities observed are expressed in S.I. units, what must be the units in which the parameter C is expressed? a. C is dimensionless (has no units) b. C must be expressed in Newtons c. C must be expressed in m/kg d. C must be expressed in m 2 /s e. C must be expressed in m 3 18. An aircraft is flying with a windspeed of 700 km/hr with a heading due west when it enters a region in which the wind is blowing toward the southwest (45 south of west) with a speed of 150 km/hr. Assume the plane s heading remains fixed (i.e. its nose continues to point toward the west). What is its speed with respect to the ground? a. 600 km/hr b. 683 km/hr c. 700 km/hr d. 765 km/hr e. 813 km/hr 19. Two balls, identical except for color, are projected horizontally from the roof of a tall building at the same instant. The initial speed of the red ball is twice the initial speed of the blue ball. Ignoring air resistance a. The red ball reaches the ground first. b. The blue ball reaches the ground first. c. Both balls land at the same instant and the blue ball has a greater speed. d. Both balls land at the same instant and the red ball has a greater speed. e. Both balls land at the same instant with the same speed.
20. A stone is thrown at an angle of 30.0 above the horizontal from the top edge of a cliff with an initial speed of 12.0 m/s. A stop watch measures the stone s trajectory time from top of cliff to bottom to be 5.60 s. What is the height of the cliff? (g = 9.8 m/s 2 and air resistance is negligible) a. 58 m b. 154 m c. 120 m d. 197 m e. 245 m 21. A ball is thrown vertically up with a speed of 15.0 m/s by a person standing on a balcony located 25.0 m above the ground. Assuming that air resistance can be neglected and that the ball hits nothing before colliding with the ground (25.0 m below its launch point) with what speed does the ball hit the ground? a. 15.0 m/s b. 18.2 m/s c. 26.7 m/s d. 39.4 m/s e. 52.6 m/s 22. At a particular instant in time a car moving along a straight East-West road has an x component of velocity of 4.5 m/s and an x component of acceleration of 1.5 m/s 2. The x axis points East. From this information you can conclude which of the following: a. The clock started 3 second earlier than the instant in question. b. The car is speeding up. c. The car is slowing down. d. The car has traveled 3.4 m since the clock was started. e. The car will come to a stop in 3 more seconds.
23. A map leading you to buried treasure instructs you to start from a particular palm tree on Gilligan s island. From the tree you are to move 4.50 m due north followed by 3.20 m west and finally 1.41 m northwest (45 N of W). How far is this final position away from the palm tree? a. 4.31 m b. 5.27 m c. 6.92 m d. 7.81 m e. 10.0 m 24. A sled with mass 12 kg is pulled horizontally by a force F across snow. A penguin of mass 8.0 kg is standing on the sled. If the coefficient of static friction between the penguin and the sled is.20 and if there is no frictional force on the bottom of the sled, what is the maximum value that F can have before the penguin slides off? a. 19 N b. 29 N c. 39 N d. 49 N e. 59 N