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1st Semester Exam Physics 2011-2012 1. A book is lying at rest on a table. The book will remain there at rest because: A) there is a net force but the book has too much inertia B) there are no forces acting on it at all C) it does move, but too slowly to be seen D) there is no net force on the book E) there is a net force, but the book is too heavy to move A book is lying at rest on a table. The book will remain there at rest because: A) there is a net force but the book has too much inertia B) there are no forces acting on it at all C) it does move, but too slowly to be seen D) there is no net force on the book E) there is a net force, but the book is too heavy to move There are forces acting on the book, but the only forces acting are in the y-direction. Gravity acts downward, but the table exerts an upward force that is equally strong, so the two forces cancel, leaving no net force. 2. Below you see two cases: a physics student pulling or pushing a sled with a force F which is applied at an angle q. In which case is the normal force greater? A) case 1 B) case 2 C) it’s the same for both D) depends on the magnitude of the force F E) depends on the ice surface Case 1 Case 2 2. Normal Force Below you see two cases: a physics student pulling or pushing a sled with a force F which is applied at an angle q. In which case is the normal force greater? A) case 1 B) case 2 C) it’s the same for both D) depends on the magnitude of the force F E) depends on the ice surface Case 1 In Case 1, the force F is pushing down (in addition to mg), so the normal force needs to be larger. In Case 2, the force F is pulling up, against gravity, so the normal force is lessened. Case 2 3. Climbing the Rope When you climb up a rope, A) this slows your initial velocity which is already upward the first thing you do is pull B) you don’t go up, you’re too heavy down on the rope. How do C) you’re not really pulling down – it just seems that way you manage to go up the rope by doing that?? D) the rope actually pulls you up E) you are pulling the ceiling down Climbing the Rope When you climb up a rope, A) this slows your initial velocity which is already upward the first thing you do is pull B) you don’t go up, you’re too heavy down on the rope. How do C) you’re not really pulling down – it just seems that way you manage to go up the rope by doing that?? D) the rope actually pulls you up E) you are pulling the ceiling down When you pull down on the rope, the rope pulls up on you!! It is actually this upward force by the rope that makes you move up! This is the “reaction” force (by the rope on you) to the force that you exerted on the rope. And voilá, this is Newton’s 3rd Law. 4. Vectors If two vectors are given A) same magnitude, but can be in any direction such that A + B = 0, what B) same magnitude, but must be in the same direction can you say about the magnitude and direction of vectors A and B? C) different magnitudes, but must be in the same direction D) same magnitude, but must be in opposite directions E) different magnitudes, but must be in opposite directions Vectors I If two vectors are given such that A + B = 0, what can you say about the magnitude and direction of vectors A and B? A) same magnitude, but can be in any direction B) same magnitude, but must be in the same direction C) different magnitudes, but must be in the same direction D) same magnitude, but must be in opposite directions E) different magnitudes, but must be in opposite directions The magnitudes must be the same, but one vector must be pointing in the opposite direction of the other, in order for the sum to come out to zero. You can prove this with the tip-to-tail method. 5. Vectors II Given that A + B = C, and that lAl 2 + lBl 2 = lCl 2, how are vectors A and B oriented with respect to each other? A) they are perpendicular to each other B) they are parallel and in the same direction C) they are parallel but in the opposite direction D) they are at 45° to each other E) they can be at any angle to each other Vectors II Given that A + B = C, and that lAl 2 + lBl 2 = lCl 2, how are vectors A and B oriented with respect to each other? A) they are perpendicular to each other B) they are parallel and in the same direction C) they are parallel but in the opposite direction D) they are at 45° to each other E) they can be at any angle to each other Note that the magnitudes of the vectors satisfy the Pythagorean Theorem. This suggests that they form a right triangle, with vector C as the hypotenuse. Thus, A and B are the legs of the right triangle and are therefore perpendicular. 6. Firing Balls I A small cart is rolling at constant velocity on a flat track. It fires a ball straight up into the air as it moves. After it is fired, what happens to the ball? A) it depends on how fast the cart is moving B) it falls behind the cart C) it falls in front of the cart D) it falls right back into the cart E) it remains at rest Firing Balls I A small cart is rolling at constant velocity on a flat track. It fires a ball straight up into the air as it moves. After it is fired, what happens to the ball? In the frame of reference of the cart, the ball only has a vertical component of velocity. So it goes up and comes back down. To a ground observer, both the cart and the ball have the same horizontal velocity, so the ball still returns into the cart. A) it depends on how fast the cart is moving B) it falls behind the cart C) it falls in front of the cart D) it falls right back into the cart E) it remains at rest when viewed from train when viewed from ground 7. Firing Balls II Now the cart is being pulled along a horizontal track by an external force (a weight hanging over the table edge) and accelerating. It fires a ball straight out of the cannon as it moves. After it is fired, what happens to the ball? A) it depends upon how much the track is tilted B) it falls behind the cart C) it falls in front of the cart D) it falls right back into the cart E) it remains at rest Firing Balls II Now the cart is being pulled along a horizontal track by an external force (a weight hanging over the table edge) and accelerating. It fires a ball straight out of the cannon as it moves. After it is fired, what happens to the ball? A) it depends upon how much the track is tilted B) it falls behind the cart C) it falls in front of the cart D) it falls right back into the cart E) it remains at rest Now the acceleration of the cart is completely unrelated to the ball. In fact, the ball does not have any horizontal acceleration at all (just like the first question), so it will lag behind the accelerating cart once it is shot out of the cannon. 8. Firing Balls III The same small cart is now rolling down an inclined track and accelerating. It fires a ball straight out of the cannon as it moves. After it is fired, what happens to the ball? A) it depends upon how much the track is tilted B) it falls behind the cart C) it falls in front of the cart D) it falls right back into the cart E) it remains at rest Firing Balls III The same small cart is now rolling down an inclined track and accelerating. It fires a ball straight out of the cannon as it moves. After it is fired, what happens to the ball? A) it depends upon how much the track is tilted B) it falls behind the cart C) it falls in front of the cart D) it falls right back into the cart E) it remains at rest Because the track is inclined, the cart accelerates. However, the ball has the same component of acceleration along the track as the cart does! This is essentially the component of g acting parallel to the inclined track. So the ball is effectively accelerating down the incline, just as the cart is, and it falls back into the cart. 9. Dropping a Package You drop a package from a plane flying at constant speed in a straight line. A) quickly lag behind the plane while falling B) remain vertically under the plane while falling Without air resistance, the C) move ahead of the plane while falling package will: D) not fall at all Dropping a Package You drop a package from a plane flying at constant speed in a straight line. A) quickly lag behind the plane while falling B) remain vertically under the plane while falling Without air resistance, the C) move ahead of the plane while falling package will: D) not fall at all Both the plane and the package have the same horizontal velocity at the moment of release. They will maintain this velocity in the x-direction, so they stay aligned. 10 Dropping the Ball I From the same height (and at the same time), one ball is dropped and another ball is fired horizontally. Which one will hit the ground first? (A) the “dropped” ball (B) the “fired” ball (C) they both hit at the same time (D) it depends on how hard the ball was fired (E) it depends on the initial height Dropping the Ball I From the same height (and at the same time), one ball is dropped and another ball is fired horizontally. Which one will hit the ground first? (A) the “dropped” ball (B) the “fired” ball (C) they both hit at the same time (D) it depends on how hard the ball was fired (E) it depends on the initial height Both of the balls are falling vertically under the influence of gravity. They both fall from the same height. Therefore, they will hit the ground at the same time. The fact that one is moving horizontally is irrelevant – remember that the x and y motions are completely independent !! 11. A) the “dropped” ball In the previous problem, B) the “fired” ball which ball has the greater C) neither – they both have the same velocity on impact velocity at ground level? D) it depends on how hard the ball was thrown Dropping the Ball II A) the “dropped” ball In the previous problem, B) the “fired” ball which ball has the greater C) neither – they both have the same velocity on impact velocity at ground level? D) it depends on how hard the ball was thrown Both balls have the same vertical velocity when they hit the ground (since they are both acted on by gravity for the same time). However, the “fired” ball also has a horizontal velocity. When you add the two components vectorially, the “fired” ball has a larger net velocity when it hits the ground. 12 A projectile is launched from the ground at an angle of 30o. At what point in its trajectory does this projectile have the least speed? A) just after it is launched B) at the highest point in its flight C) just before it hits the ground D) halfway between the ground and the highest point E) speed is always constant 12 A projectile is launched from the ground at an angle of 30o. At what point in its trajectory does this projectile have the least speed? A) just after it is launched B) at the highest point in its flight C) just before it hits the ground D) halfway between the ground and the highest point E) speed is always constant The speed is smallest at the highest point of its flight path because the ycomponent of the velocity is zero. 13. Suppose a projectile is launched straight up. Make a statement about the velocity and the acceleration when the projectile reaches the highest point. A) Both its velocity and its acceleration are zero. B) Its velocity is zero and its acceleration is not zero. C) Its velocity is not zero and its acceleration is zero. D) Neither its velocity nor its acceleration is zero. 14 Up in the Air I You throw a ball upward with A) more than 10 m/s an initial speed of 10 m/s. B) 10 m/s Assuming that there is no air resistance, what is its speed when it returns to you? C) less than 10 m/s D) zero E) need more information 14 You throw a ball upward with A) more than 10 m/s an initial speed of 10 m/s. B) 10 m/s Assuming that there is no air resistance, what is its speed when it returns to you? C) less than 10 m/s D) zero E) need more information The ball is slowing down on the way up due to gravity. Eventually it stops. Then it accelerates downward due to gravity (again). Since a = g on the way up and on the way down, the ball reaches the same speed when it gets back to you as it had when it left. 15) Four students measure the mass of an object, each using a different scale. They record their results as follows: Which student used the least precise scale? A) A Student A B C D Mass (g ) 49.06 49 50 49.2 B) B C) C D) D 16. All of the following are base units of the SI system except: A) kilogram. B) kelvin. C) meter. D) volt. 17. Select the list which contains only SI basic units. A) liter, meter, second, watt B) joule, kelvin, kilogram, watt C) candela, kelvin, meter, second D) joule, newton, second, watt 18. The number of significant figures in 10001 is A) two. B) three. C) five. D) six. 19. Suppose that an object travels from one point in space to another. Make a comparison between the displacement and the distance traveled. A) The displacement is either greater than or equal to the distance traveled. B) The displacement is always equal to the distance traveled. C) The displacement is either less than or equal to the distance traveled. D) The displacement can be either greater than, smaller than, or equal to the distance traveled. 20. When is the average velocity of an object equal to the instantaneous velocity? A) always B) never C) only when the velocity is constant D) only when the velocity is increasing at a constant rate 21 You drive for 30 minutes at 30 A) more than 40 mi/hr mi/hr and then for another 30 B) equal to 40 mi/hr minutes at 50 mi/hr. What is your average speed for the whole trip? C) less than 40 mi/hr 21 You drive for 30 minutes at 30 A) more than 40 mi/hr mi/hr and then for another 30 B) equal to 40 mi/hr minutes at 50 mi/hr. What is your C) less than 40 mi/hr average speed for the whole trip? It is 40 mi/hr in this case. Since the average speed is distance/time and you spend the same amount of time at each speed, then your average speed would indeed be 40 mi/hr. 22. A polar bear starts at the North Pole. It travels 1.0 km south, then 1.0 km east, then 1.0 km north, then 1.0 km west to return to its starting point. This trip takes 45 min. What was the bear's average speed? A) 0 km/h B) 0.09 km/h C) 4.5 km/h D) 5.3 km/h 23. The number of significant figures in 0.01500 is A) two. B) three. C) four. D) five. 24. A cart starts from rest and accelerates at 4.0 m/s2 for 5.0 s, then maintain that velocity for 10 s, and then decelerates at the rate of 2.0 m/s2 for 4.0 s. What is the final speed of the car? A) 20 m/s B) 16 m/s C) 12 m/s D) 10 m/s 25. An object is thrown upward with a speed of 14 m/s on the surface of planet X where the acceleration due to gravity is 3.5 m/s2. What is the speed of the object after 8.0 s? A) 7.0 m/s B) 14 m/s C) 21 m/s D) 64 m/s 26. In the figure, what is the velocity at t = 1.0 s? A) 0 B) 10 m/s C) 20 m/s D) -40 m/ 27. In Fig. 2-1, what is the velocity at t = 2.5 s? A) 0 B) 10 m/s C) 20 m/s D) -40 m/s 28. InInFig. Fig.2-1, 2-1,what what velocity = 4.0 28. is is thethe velocity at tat= t4.0 s? s? A) 0 B) 10 m/s C) 20 m/s D) -40 m/s 29. What is the product of 12.56 and 2.12? A) 27 B) 26.6 C) 26.23 D) 26.627 30. Which of the following is an accurate statement? A vector cannot have magnitude if one A) A) A vector cannot have zerozero magnitude if one of its of its components components is not zero. is not zero. The magnitude vectorcan canbe beless lessthan thanthe the B) B) The magnitude ofofa avector magnitude of one of its components. magnitude of one of its components. C) If the magnitude of vector A is less than the C) Ifmagnitude the magnitude of vector A the is less than the of of vector B, then x-component magnitude of than vector then the x-component of A is A is less theB, x-component of B. lessD)than x-component of B.can be positive or Thethe magnitude of a vector negative. D) The magnitude of a vector can be positive or negative. 31. What is the result of 2.43 ÷ 4.561? A) 5.3278 × 10-1 B) 5.328 × 10-1 C) 5.33 × 10-1 D) 5.3 × 10-1 32. When you sit on a chair, the resultant force on you is A) zero. B) up. C) down. D) depending on your weight. 33. The radius of the Earth is 3963 mi. What is the surface area of the Earth in square meters? (1 mi = 1609 m.) A) 4.9 × 107 m2 B) 1.3 × 1014 m2 C) 2.6 × 1014 m2 D) 5.1 × 1014 m2 34. A 400-m tall tower casts a 600-m long shadow over a level ground. At what angle is the Sun elevated above the horizon? A) 34° B) 42° C) 48° D) can't be found; not enough information 35. If you blow up a balloon, and then release it, the balloon will fly away. This is an illustration of A) Newton's 1st law. B) Newton's 2nd law. C) Newton's 3rd law. D) Galileo's law of inertia. 36. Two displacement vectors have magnitudes of 5.0 m and 7.0 m, respectively. When these two vectors are added, the magnitude of the sum A) is 2.0 m. B) could be as small as 2.0 m, or as large as 12 m. C) is 12 m. D) is larger than 12 m. 37. A ball is thrown upward at a velocity 37. of A 19.6 ball is thrown at a velocity m/s. Whatupward is its velocity after of 19.6 m/s. What is3.00 its velocity after 3.00 s? s? A) 9.8 m/s upward B) 9.8 m/s downward C) zero D) 19.6 downward 38. The acceleration of gravity on the Moon is only one-sixth of that on Earth. If you hit a baseball on the Moon with the same effort (and at the speed and angle) that you would on Earth, the ball would land A) the same distance away. B) one-sixth as far. C) 6 times as far. D) 36 times as far. 39. A runner runs halfway around a circular path of radius 10 m. What is the displacement of the jogger? A) 0 B) 5 m C) 10 m D) 20 m 40. In the Figure on the right, what is the average velocity from 0 to 6.0 s? A) 0 B) 10 m/s C) 20 m/s D) -40 m/s 41. In Fig. 2-2, what is the acceleration at 3.0 s? A) 0 B) 2.0 m/s2 C) -2.5 m/s2 D) 10 m/s2 42. In Fig. 2-2, what is the average acceleration from 0 to 8.0 s? A) 0 B) 2.0 m/s2 C) -2.5 m/s2 D) 10 m/s2 43. In Fig. 2-2, what is the displacement from 0 to 8.0 s? A) 20 m B) 40 m C) 60 m D) 80 m 44. In the diagram shown below, the unknown vector is A) B) C) D) 45. Ignoring air resistance, the horizontal component of a projectile's velocity A) is zero. B) remains constant. C) continuously increases. D) continuously decreases. 46. A pilot drops a bomb from a plane flying horizontally at a constant speed. Neglecting air resistance, when the bomb hits the ground the horizontal location of the plane will A) be behind the bomb. B) be over the bomb. C) be in front of the bomb. D) depend on the speed of the plane when the bomb was released. 47. What is the mass of an object that weighs 250 N on the surface of the Earth where the acceleration due to gravity is 9.80 m/s2? A) 250 kg B) 24.5 kg C) 25.5 kg D) 2,450 kg 48. Can work be done on a system if there is no motion? A) Yes, if an outside force is provided. B) Yes, since motion is only relative. C) No, since a system which is not moving has no energy. D) No, because of the way work is defined. 49. A container of water is lifted vertically 3.0 m then returned to its original position. If the total weight is 30 N, how much work was done? A) 45 J B) 90 J C) 180 J D) No work was done. 50. Does the centripetal force acting on an object do work on the object? A) Yes, since a force acts and the object moves, and work is force times distance. B) Yes, since it takes energy to turn an object. C) No, because the object has constant speed. D) No, because the force and the displacement of the object are perpendicular. 51. A person is standing on a scale in an elevator accelerating downward. Compare the reading on the scale to the person's true weight. A) greater than their true weight B) B) equal to their true weight C) less than their true weight D) zero 52. Is it possible for an object moving with a constant speed to accelerate? Explain. A) No, if the speed is constant then the acceleration is equal to zero. B) No, an object can accelerate only if there is a net force acting on it. C) Yes, although the speed is constant, the direction of the velocity can be changing. D) Yes, if an object is moving it can experience acceleration 53. A force moves an object in the direction of the force. The graph to the right, shows the force versus the object's position. Find the work done when the object moves from 0 to 2.0 m. A) 20 J B) 40 J C) 60 J D) 80 J 54. A force moves an object in the direction of the force. The graph shows the force versus the object's position. Find the work done when the object moves from 2.0 to 4.0 m. A) 20 J B) 40 J C) 60 J D) 80 J 55. A force moves an object in the direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 4.0 to 6.0 m. A) 20 J B) 40 J C) 60 J D) 80 J 56. List the four fundamental forces in nature. A) gravitational, normal, tension, friction B) gravitational, normal, kinetic friction, static friction C) gravitational, electromagnetic, strong nuclear, weak nuclear D) gravitational, electromagnetic, contact, nuclear 57. A spherically symmetric planet has four times the Earth's mass and twice its radius. If a jar of peanut butter weighs 12 N on the surface of the Earth, how much would it weigh on the surface of this planet? A) 6.0 N B) 12 N C) 24 N D) 36 N 58. Which of Newton's laws best explains why motorists should buckle-up? A) the first law B) the second law C) the third law D) the law of gravitation 59. Two forces are acting on an object as shown in the figure. What is the magnitude of the resultant force? A) 47.5 N B) 185 N C) 198 N D) 200 N 60. Two forces are acting on an object as shown the figure.. What is the direction of the resultant force? A) 12° above -x B) 78° above -x C) 12° above +x D) 78° above +x 61. The speed of Halley's Comet, while traveling in its elliptical orbit around the Sun, A) is constant. B) increases as it nears the Sun. C) decreases as it nears the Sun. D) is zero at two points in the orbit. 62. 63. Calculate the average velocity 64. Calculate the average acceleration