1st Semester Exam Physics 2011-2012

1. 1st Semester Exam Physics 2011-2012

2. 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 1. A book is lying at rest on a table. The book will remain there at rest because:

3. 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: 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.

4. Case 1 Case 2 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 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?

5. 2. Normal Force Case 1 Case 2 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 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? 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.

6. 3. Climbing the Rope A) this slows your initial velocity which is already upward B) you don’t go up, you’re too heavy C) you’re not really pulling down – it just seems that way D) the rope actually pulls you up E) you are pulling the ceiling down When you climb up a rope, the first thing you do is pull down on the rope. How do you manage to go up the rope by doing that??

7. Climbing the Rope A) this slows your initial velocity which is already upward B) you don’t go up, you’re too heavy C) you’re not really pulling down – it just seems that way D) the rope actually pulls you up E) you are pulling the ceiling down When you climb up a rope, the first thing you do is pull down on the rope. How do you manage to go up the rope by doing that?? 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 therope. And voilá, this is Newton’s 3rd Law.

8. 4. Vectors 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 If two vectors are given such that A + B = 0, what can you say about the magnitude and direction of vectors A and B?

9. Vectors I 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 If two vectors are given such that A + B = 0, what can you say about the magnitude and direction of vectors A and B? 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.

10. 5.Vectors II 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 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?

11. Vectors II 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 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? Note that the magnitudes of the vectors satisfy the Pythagorean Theorem. This suggests that they form a right triangle, with vectorCas the hypotenuse. Thus,AandBare the legs of the right triangle and are therefore perpendicular.

12. 6.Firing Balls I 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 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?

13. Firing Balls I when viewed from train when viewed from ground 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 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.

14. 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

15. 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.

16. 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

17. 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 thesame component of accelerationalong the track as the cart does! This is essentially the component ofgacting 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.

18. 9. Dropping a Package A) quickly lag behind the plane while falling B) remain vertically under the plane while falling C) move ahead of the plane while falling D) not fall at all You drop a package from a plane flying at constant speed in a straight line. Without air resistance, the package will:

19. Dropping a Package A) quickly lag behind the plane while falling B) remain vertically under the plane while falling C) move ahead of the plane while falling D) not fall at all You drop a package from a plane flying at constant speed in a straight line. Without air resistance, the package will: Both the plane and the package have the samehorizontalvelocity at the moment of release. They will maintain this velocity in the x-direction, so they stay aligned.

20. 10Dropping the Ball I (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 From the sameheight (and at the sametime), one ball is dropped and another ball is fired horizontally. Which one will hit the ground first?

21. Dropping the Ball I (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 From the sameheight (and at the sametime), one ball is dropped and another ball is fired horizontally. Which one will hit the ground first? 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 !!

22. 11. A) the “dropped” ball B) the “fired” ball C) neither – they both have the same velocity on impact D) it depends on how hard the ball was thrown In the previous problem, which ball has the greater velocity at ground level?

23. Dropping the Ball II A) the “dropped” ball B) the “fired” ball C) neither – they both have the same velocity on impact D) it depends on how hard the ball was thrown In the previous problem, which ball has the greater velocity at ground level? 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.

24. 12 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 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?

25. 12 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 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? The speed is smallest at the highest point of its flight path because the y-component of the velocity is zero.

26. 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.

27. 14 Up in the Air I A) more than 10 m/s B) 10 m/s C) less than 10 m/s D) zero E) need more information You throw a ball upward with an initial speed of 10 m/s. Assuming that there is no air resistance, what is its speed when it returns to you?

28. 14 A) more than 10 m/s B) 10 m/s C) less than 10 m/s D) zero E) need more information You throw a ball upward with an initial speed of 10 m/s. Assuming that there is no air resistance, what is its speed when it returns to you? 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.

29. 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 B) B C) C D) D

30. 16. All of the following are base units of the SI system except: A) kilogram. B) kelvin. C) meter. D) volt.

31. 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

32. 18. The number of significant figures in 10001 is A) two. B) three. C) five. D) six.

33. 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.

34. 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

35. 21 A) more than 40 mi/hr B) equal to 40 mi/hr C) less than 40 mi/hr You drive for 30 minutes at 30 mi/hr and then for another 30 minutes at 50 mi/hr. What is your average speed for the whole trip?

36. 21 A) more than 40 mi/hr B) equal to 40 mi/hr C) less than 40 mi/hr You drive for 30 minutes at 30 mi/hr and then for another 30 minutes at 50 mi/hr. What is your 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.

37. 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

38. 23. The number of significant figures in 0.01500 is A) two. B) three. C) four. D) five.

39. 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

40. 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

41. 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/

42. 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

43. 28. In Fig. 2-1, what is the velocity at t = 4.0 s? 28. In Fig. 2-1, what is the velocity at t = 4.0 s? A) 0 B) 10 m/s C) 20 m/s D) -40 m/s

44. 29. What is the product of 12.56 and 2.12? A) 27 B) 26.6 C) 26.23 D) 26.627

45. 30. Which of the following is an accurate statement? A) A vector cannot have zero magnitude if one of its components is not zero. B) The magnitude of a vector can be less than the magnitude of one of its components. C) If the magnitude of vector A is less than the magnitude of vector B, then the x-component of A is less than the x-component of B. D) The magnitude of a vector can be positive or negative. A) A vector cannot have zero magnitude if one of its components is not zero. B) The magnitude of a vector can be less than the magnitude of one of its components. C) If the magnitude of vector A is less than the magnitude of vector B, then the x-component of A is less than the x-component of B. D) The magnitude of a vector can be positive or negative.

46. 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

47. 32. When you sit on a chair, the resultant force on you is A) zero. B) up. C) down. D) depending on your weight.

48. 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

49. 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

50. 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.