MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

Transcription

1 MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) Vector A has length 4 units and directed to the north. Vector B has length 9 units and is directed to the south. Calculate the magnitude and direction of A + B. A) 13 units, north B) 13 units, south C) 5 units, south D) 5 units, north 2) If you were to move into outer space far from any stars or planets, A) your weight would change, but your mass would not change. B) your mass would change, but your weight would not change. C) neither your weight nor your mass would change. D) both your weight and mass would change. E) None of these is true. 1) 2) 3) A child on a sled starts from rest at the top of a 15.0 slope. If the trip to the bottom takes 15.2 s how long is the slope? Assume that frictional forces may be neglected. A) 147 m B) 586 m C) 293 m D) 1130 m 3) 4) Which of the following ideas is true about projectile motion with no air drag? 4) A) ν 2 x + ν 2 y = constant. B) The trajectory will depend on the objectʹs mass as well as its initial velocity and launch angle. C) The velocity of the object is zero at the point of maximum elevation. D) The acceleration is +g when the object is rising and -g when falling. E) The horizontal motion is independent of the vertical motion. 5) A large truck collides head-on with ʺBettyʺ bumbelbee. During the collision A) the truck exerts a smaller amount of force on the bee than the bee exerts on the truck. B) the truck exerts the same amount of force on the bee as the bee exerts on the truck. C) the truck exerts a greater amount of force on the bee than the bee exerts on the truck. D) the truck exerts a force on the bee, but the bee exerts no force on the truck. 5) 6) It takes 4500 N to accelerate a car at a rate of 3.42 m/s2. What is the mass of the car? A) 1310 kg B) 1700 kg C) 1040 kg D) 1510 kg 6) 7) A ball is thrown straight upward with a velocity of 39 m/s. How much time passes before the ball strikes the ground? (Disregard air resistance.) A) 8.0 s B) 2.4 s C) 1.2 s D) 4.0 s 7) 8) A ball is thrown vertically upward and then comes back down. During the ballʹs flight up and down, its velocity and acceleration vectors are A) always in opposite directions. B) first in opposite directions and then in the same direction. C) always in the same direction. D) first in the same direction and then in opposite directions. 8) 1

2 9) Shown here are the velocity and acceleration vectors for an object in several different types of motion. In which case is the object s velocity changing while its speed is not changing? A) 9) B) C) D) E) None of these cases 10) Consider what happens when you jump up in the air. Which of the following is the most accurate statement? A) When you push down on the earth with a force greater than your weight, the earth will push back with the same magnitude force and thus propel you into the air. B) Since the ground is stationary, it cannot exert the upward force necessary to propel you into the air. Instead, it is the internal forces of your muscles acting on your body itself which propels the body into the air. C) You are able to spring up because the earth exerts a force upward on you which is stronger than the downward force you exert on the earth. D) It is the upward force exerted by the ground that pushes you up, but this force can never exceed your weight. 10) 11) A CD-ROM disk can store approximately megabytes of information. If an average word requires 9.0 bytes of storage, how many words can be stored on one disk? A) words B) words C) words D) words 11) 12) Suppose you are playing hockey on a new-age ice surface in which there is no friction between the ice and the hockey puck. You wind up and hit the puck as hard as you can. Just after the puck loses contact with your stick, the puck A) will speed up a little, and then move at a constant speed. B) will speed up a little, and then slow down. C) will not slow down or speed up. D) will start to slow down. 12) 2

3 13) The following conversion equivalents are given: 1 m = 100 cm 1 in = 2.54 cm 1 ft = 12 in A bin has a volume of 1.5 m3. The volume of the bin, in ft3, is closest to: A) 47 B) 59 C) 41 D) 35 E) 53 13) 14) Which of the following is NOT a vector? A) velocity B) speed C) acceleration D) displacement 14) 15) If you jumped out of a plane, you would begin speeding up as you fall downward. Eventually, due to wind resistance, your velocity would become constant with time. After this occurs, the magnitude of the force of wind resistance is A) equal to the force of gravity acting on you. B) is greater than the force of gravity acting on you. C) is slightly smaller than the force of gravity acting on you. D) is much smaller than the force of gravity acting on you. 15) 16) A skydiver reaches a ʺterminal velocityʺ of 120 km/h. If the skydiver has a mass of 59.0 kg, what is the magnitude of the upward force on the skydiver due to wind resistance? (Use g = 9.8 m/s2.) A) 5.42 N B) 6.02 N C) 578 N D) 636 N 16) 17) Two identical objects A and B fall from rest from different heights to the ground. If object B takes twice as long as A to reach the ground, what is the ratio of the heights from which A and B fell? Neglect air resistance. A) 1 : 2 B) 1 : 4 C) 1 : 2 D) 1 : 8 17) 18) Acceleration is sometimes expressed in multiples of g, where g = 9.8 m/s2 is the acceleration due to the earthʹs gravity. In a car crash, the carʹs velocity may go from 26 m/s to 0 m/s in 0.15 s. How many gʹs are experienced, on average, by the driver? A) 22 g B) 23 g C) 18g D) 13 g 18) 19) A car accelerates from 5.0 m/s to 21 m/s at a rate of 3.0 m/s2. How far does it travel while accelerating? A) 117 m B) 207 m C) 69m D) 41 m 19) 3

4 20) A child standing on a bridge throws a rock straight down (HINT: initial velocity in the negative y direction!). The rock leaves the childʹs hand at t = 0. Which of the graphs shown here best represents the velocity of the stone as a function of time? A) 20) B) C) D) E) 21) The magnitude of A is 5.5. Vector A lies in the second quadrant and forms an angle of 34 degrees with the y-axis. The components, Ax and Ay, are closest to: A) Ax = +4.6, Ay = -3.1 B) Ax = -4.6, Ay = -3.1 C) Ax = -4.6, Ay = +3.1 D) Ax = -3.1, Ay = +4.6 E) Ax = +3.1, Ay = ) 22) Joe and Bill are playing tug-of-war. Joe is pulling with a force of 200 N. Bill is simply hanging on to the rope. Neither person is moving. What is the tension of the rope? A) 200 N B) 300 N C) 400 N D) 0 N 22) 4

5 23) A fisherman casts his bait into the river at an angle of 25. As the line unravels, he notices that the bait and hook reach a maximum height of 3.9 m. What was the initial velocity he launched the bait with? A) 8.4 m/s B) 9.2 m/s C) 21 m/s D) 10 m/s 23) 24) Two bullets are fired simultaneously parallel to a horizontal plane. The bullets have different masses and different initial velocities. Which one will strike the plane first? A) the heaviest one B) the slowest one C) the lightest one D) the fastest one E) They strike the plane at the same time. 24) 25) A boy throws a rock with an initial velocity of 3.13 m/s at 30.0 above the horizontal. How long does it take for the rock to reach the maximum height of its trajectory? A) s B) s C) s D) s 25) 26) The plot below shows the position of an object as a function of time. The letters H-L represent particular moments of time. At which moment in time is the speed of the object equal to zero? 26) A) I B) H C) J D) K E) L 27) A small boat is moving at a velocity of 3.35 m/s when it is accelerated by a river current perpendicular to the initial direction of motion. If the current acceleration is m/s2, what will the new velocity of the boat be after 33.5 s? A) 25.3 m/s at 7.59 from initial direction of motion B) 25.3 m/s at 82.4 from initial direction of motion C) m/s at 7.59 from initial direction of motion D) m/s at 82.4 from initial direction of motion 27) Extra Bonus: Answers the question. 28) You are in a elevator which starts accelerating upward. Explain what happens to your apparent weight, and why. 28) 5

6 29) What is the minimum number of vectors (none of which have the same magnitude) for which it is theoretically possible that the sum of those vectors can be equal to zero? 29) 30) Three children pull on a toy in three different directions, yet the toy does not move. Explain how this could be possible. 30) 6

7 Answer Key Testname: 201_SUMMER2009_1_V3 1) C 2) A 3) C 4) E 5) B 6) A 7) A 8) B 9) A 10) A 11) D 12) C 13) E 14) B 15) A 16) C 17) B 18) C 19) C 20) C 21) D 22) A 23) C 24) E 25) C 26) A 27) B 28) Your apparent weight will increase. Since your apparent weight is equal in magnitude to the reaction force N which you experience: ΣFy = ma (upward acceleration is positive) N - mg = ma N = m(g + a) Thus N is larger when accelerating upward. 29) It is possible with three (or more) vectors. Three is the minimum number for which the condition may be satisfied. 30) As long as the vector sum of all of the individual forces is equal to zero, there is no net force on the toy, so it does not move. 7