Physics P201 D. Baxter/R. Heinz

Transcription

1 Seat # Physics P201 D. Baxter/R. Heinz EXAM #1 September 20, :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.

2 1. A book rests on a table, exerting a downward force on the table. The reaction to this force is: a. the force of the Earth on the book b. the force of the table on the book c. the force of the Earth on the table d. the force of the book on the Earth e. The inertia of the book 2. When we subtract a velocity vector from another velocity vector, the result is: a. another velocity b. an acceleration c. a displacement d. a scalar e. a time interval 3. Note the expression: y = x 2. Which statement is most consistent with this expression? a. y is less than x b. if y doubles, then x quadruples c. y is greater than x d. if x doubles, then y doubles e. if x doubles, then y quadruples 4. A rock is thrown straight up with an initial velocity of 19.6 m/s. What time interval elapses between the rock s release and its return to the original launch point? a. 2.0 s b. 4.0 s c. 5.0 s d. 8.0 s e s

3 5. Omar throws a rock directly downward with speed 12 m/s from the top of a tower. The rock hits the ground after 2.0 s. What is the height of the tower? (Air resistance is negligible.) a. 20 m b. 24 m c. 44 m d. 63 m e. 72 m 6. The diagram represents the velocity for the straight line motion of a car as a function of time. Which of the following statements is true? a. The car accelerates, stops, and reverses b. The car accelerates at 6 m/s 2 for the first 2 s c. The car is moving for a total time of 12 s d. The car decelerates at 12 m/s 2 for the last 4 s e. The car returns to its starting point when t 9 s 7. An automobile of mass 2000 kg moving at 30 m/s, is braked suddenly, with a constant braking force of 10,000 N. How far does the car travel before stopping? a. 45 m b. 90 m c. 135 m d. 190 m e. 240 m 8. Assume everyone in the United States consumes one soft drink in an aluminum can every two days. If there are 270 million Americans, how many tons of aluminum are available for recycling from this source alone each year if each can weighs 1/16 pound and one ton = 2000 pounds? a. 250,000 tons b. 750,000 tons c. 1.5 million tons d million tons e. 3 million tons

4 9. A baseball is thrown by the centerfielder (from shoulder level) to home plate where it is caught (on the fly at shoulder level) by the catcher. At what point during the flight is the ball s speed at a minimum? (Resistance is negligible.) a. just after leaving the centerfielder s hand b. just before arriving at the catcher s mitt c. speed is constant during entire trajectory d. it depends on the angle at which the center fielder throws the ball e. at the top of the trajectory 10. A helicopter is traveling at 40 m/s at a constant altitude of 100 m over a level field. If a wheel falls off the helicopter, with what velocity will it hit the ground? (assume that air resistance negligible) a. 40 m/s b. 50 m/s c. 60 m/s d. 70 m/s e. 80 m/s 11. A bridge that was 5.0 m long has been washed out by the rain several days ago. What is the approximate minimum speed that a motorcycle must be going to successfully jump the stream? Although the road is level on both sides of the bridge, the road on the far side is 2.0 m lower than the road on this side. 2.0m 5.0m a. 5.0 m/s b. 7.8 m/s c m/s d. 13 m/s e. 25 m/s

5 12. Two ropes are attached to a 40 kg object. The first rope applies a force of 25 N and the second 40 N. If the two ropes are perpendicular to each other and no other net force acts on the object, what is the magnitude of the resultant acceleration of the object? a. 1.2 m/s 2 b. 3.0 m/s 2 c. 6.3 m/s 2 d. 9.8 m/s 2 e m/s It is late and Carlos is sliding down a rope from his third floor window to meet his friend Juan. As he slides down the rope faster and faster, he becomes frightened and grabs harder on the rope, increasing the tension in the rope. As soon as the upward tension in the rope becomes equal to his weight: a. Carlos will stop. b. Carlos will slow down. c. Carlos will speed up. d. Carlos will continue down at a constant velocity. e. The rope must break. 14. A 9.00 kg hanging weight is connected by a massless string over a frictionless pulley to a 5.00 kg block sliding on a flat table. If the coefficient of sliding friction is 0.150, find the magnitude of the acceleration of the 9.00 kg block. a m/s 2 b m/s 2 c m/s 2 d m/s 2 e m/s 2 5 kg T 9 kg

6 15. Which of the curves on the graph below best represents v y vs. t, where v y is the y component of the velocity and the y-axis points up, for a projectile fired at an angle of 45, above the horizontal? a. OC b. DE c. AF d. AB e. AE 16. Dana uses a rope to pull a box that weighs 300 N across a level surface with constant velocity. The rope makes an angle of 30 above the horizontal and the tension in the rope is 100 N. What is the coefficient of friction? a b c d e N 30 o T=100N 17. A 5000 N weight is held suspended in equilibrium by two cables. Cable 1 applies a horizontal force to the right of the object and has a tension, T 1. Cable 2 applies a force upward and to the left at an angle of 37 to the horizontal and has a tension, T 2. What is the tension, T 1? a N b N c N d N e N T 2 37 o T N

7 18. Find the tension in an elevator cable if the 1000 kg elevator it supports is descending with an acceleration of 1.8 m/s 2, downward. a. 4,200 N b. 5,700 N c. 8,000 N d. 9,800 N e. 11,600 N 19. A European sports car dealer claims that his product will accelerate at a constant rate from rest to a speed of km/hr in 8.00 s. What is the speed after the first 5.00 s of acceleration? (First convert the speed to m/s.) a m/s b m/s c m/s d m/s e m/s 20. A large truck breaks down out on the road and receives a push back into town by a small compact car as shown in the figure below. While the car, still pushing the truck, is speeding up to get up to cruising speed, a. the amount of force with which the car pushes on the truck is equal to that with which the truck pushes back on the car. b. the amount of force with which the car pushes on the truck is smaller than that with which the truck pushes back on the car. c. the amount of force with which the car pushes on the truck is greater than that with which the truck pushes back on the car. d. the car s engine is running so the car pushes against the truck, but the truck s engine is not running so the truck cannot push back against the car. The truck is pushed forward simply because it is in the way of the car. e. neither the car nor the truck exerts any force on the other. The truck is pushed forward simply because it is in the way of the car.

8 Consider the situation below in answering questions 21 and 22. A boy wishes to row across a river from New Jersey to New York. He can row at 2 m/s in still water and the river is flowing at 1 m/s. 21. At what angle 4 with respect to the shore should he point the bow (front) of his boat to travel perpendicular to the shore? a. 18, b. 36, c. 45, d. 60, e. 75, 22. At what angle 4 with respect to the shore should he point the bow (front) of his boat to cross the river in the shortest possible time? a. 36, b. 45, c. 60, d. 75, e. 90, 23. If a is acceleration, v is velocity, x is position, and t is time, then which equation is not dimensionally correct? a. t = x/v b. a = v 2 /x c. t 2 = 2x/a d. v 2 =2ax e. v = a/t THERE IS ONE MORE QUESTION ON THE NEXT PAGE!!

9 24. A vehicle designed to operate on a drag strip accelerates from zero to 30.0 m/s while undergoing a straight line path displacement of 45.0 m. What is the vehicle s constant acceleration? a. 1.5 m/s 2 b. 2.0 m/s 2 c. 5.0 m/s 2 d m/s 2 e m/s 2