Physics midterm

94. A ball thrown horizontally from a point 24 m above the ground, strikes the ground after traveling horizontally a distanc e of 18 m. With what speed was it thrown?

c. 8.1 m/ s

12. Suppose a can, after an initial kick, moves up along a smooth hill of ice. Make a statement concerning its acceleration.

c. It will have the same acceleration, both up the hill and down the hill.

Suppose that an object travels from one point in space to another. Make a comparison between the displacement and the distance traveled.

c. The displacement is either less than or equal to the distance traveled.

28. A brick is dropped from the top of a building. A second brick is thrown straight down from the same building. They are released at the same time. Neglect air resistance. Compare the accelerations of the two bricks.

c. The two bricks accelerate at the same rate.

27. Two objects are thrown from the top of a tall building. One is thrown up, and the other is thrown down, both with the same initial speed. What are their speeds when they hit the street?

c. They are traveling at the same speed.

70. A bullet is fired horizontally, and at the same instant a second bullet is dropped from the same height. Ignore air resistance. Compare the times of fall of the two bullets.

c. They hit at the same time.

9. Can an object's velocity change direction when its acceleration is constant? Support your ANS with an example.

c. Yes, this is possible, and a rock thrown straight up is an example.

29. An object is moving with constant non-zero velocity in the +x axis. The position versus time graph of this object is

c. a straight line making an angle with the time axis.

32. An object is moving with constant non-zero acceleration in the +x axis. The velocity versus time graph of this object is

c. a straight line making an angle with the time axis.

34. The slope of a velocity versus time graph gives

c. acceleration.

37. If the position versus time graph of an object is a horizontal line, the object

c. at rest.

3. A new car manufacturer advertises that their car can go "from zero to sixty in 8 s". This is a description of

c. average acceleration.

43. Select the list which contains only SI basic units.

c. candela, kelvin, meter, second

36. The area under a curve in a velocity versus time graph gives

c. displacement.

19. Suppose a ball is thrown straight up. What is its acceleration just before it reaches its highest point?

c. exactly g

72. A package of supplies is dropped from a plane, and one second later a second package is dropped. Neglecting air resistance, the distance between the falling packages will

c. increase.

47. The metric prefix for one thousand is

c. kilo.

2. When is the average velocity of an object equal to the instantaneous velocity?

c. only when the velocity is constant

44. The base SI unit of time is

c. second.

63. If the acceleration vector of an object is directed anti-parallel to the velocity vector,

c. the object is slowing down.

64. If the acceleration of an object is always directed perpendicular to its velocity,

c. the object is turning.

53. If you are 5'10'' tall, what is your height in meters? (1 in = 2.54 cm.)

d. 1.8 m

81. A boat, whose speed in still water is 8.0 m/ s, is directed across a river with a current of 6.0 m/ s. What is the speed of the boat as it crosses the river?

d. 10.0 m/ s

58. The resultant of two vectors is the smallest when the angle between them is

d. 180°.

93. A runner runs halfway around a circular path of radius 10 m. What is the displacement of the jogger?

d. 20 m

66. An Olympic athlete throws a javelin at four different angles above the horizontal, each with the same speed: 30°, 40°, 60°, and 80°. Which two throws cause the javelin to land the same distance away?

d. 30° and 60°

96. A projectile is launched with an initial velocity of 60.0 m/ s at an angle of 30.0° above the horizontal. How far does i t travel?

d. 318 m

54. A hot air balloon rises to an altitude of 600 fathoms. What is this height, in feet? (1 fathom = 6 ft.)

d. 3600 ft

92. If vector = (-3.0, -4.0) and vector = (+3.0, -8.0), what is the magnitude of vector = - ?

d. 7.2

21. A ball is thrown straight up, reaches a maximum height, then falls to its initial height. Make a statement about the direction of the velocity and acceleration as the ball is coming down.

d. Both its velocity and its acceleration point downward.

16. When an object is released from rest and falls in the absence of friction, which of the following is true concerning its motion?

d. None of the above is true.

7. Suppose that an object is moving with a constant velocity. Make a statement concerning its acceleration.

d. The acceleration must be equal to zero.

11. Can an object have increasing speed while its acceleration is decreasing? Support your ANS with an example.

d. Yes, and an example would be an object released from rest in the presence of air friction.

30. An object is moving with constant non-zero acceleration in the +x axis. The position versus time graph of this object is

d. a parabolic curve.

15. Objects A and B both start from rest. They both accelerate at the same rate. However, object A accelerates for twice the time as object B. What is the distance traveled by object A compared to that of object

d. four times as far

67. You are throwing a ball for the second time. If the ball leaves your hand with twice the velocity it had on your first throw, its horizontal range R (compared to your first serve) would be

d. four times as much.

75. You are trying to cross a river that flows due south with a strong current. You start out in your motorboat on the east bank desiring to reach the west bank directly west from your starting point. You should head your motorboat

d. in a northwesterly direction.

4. An object moving in the +x axis experiences an acceleration of 2.0 m/ s2. This means the object is

d. increasing its velocity by 2.0 m/ s in every second.

38. If the position versus time graph of an object is a vertical line, the object is

d. moving with infinite speed.

42. All of the following are base units of the SI system except:

d. volt.

84. A swimmer heading directly across a river 200 m wide reaches the opposite bank in 6 min 40 s. She is swept downstream 480 m. How fast can she swim in still water?

a. 0.50 m/ s

60. A ball is thrown with a velocity of 20 m/ s at an angle of 60° above the horizontal. What is the horizontal component of its instantaneous velocity at the exact top of its trajectory?

a. 10 m/ s

71. A plane flying horizontally at a speed of 50.0 m/ s and at an elevation of 160 m drops a package. Two seconds later it drops a second package. How far apart will the two packages land on the ground?

a. 100 m

50. Select the smallest value.

a. 15 × 10-3

87. If you walk 6.0 km in a straight line in a direction north of east and you end up 2.0 km north and several kilometers ea st. How many degrees north of east have you walked?

a. 19°

76. Your motorboat can move at 30 km/ h in still water. How much time will it take you to move 12 km downstream, in a river flowing at 6.0 km/ h?

a. 20 min

80. A fighter plane moving 200 m/ s horizontally fires a projectile with speed 50.0 m/ s in a forward direction 30.0° below the horizontal. What is the speed of the projectile with respect to a stationary observer on the ground?

a. 245 m/ s

89. 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°

51. Write the number 0.00045 in power of ten notation.

a. 4.5 × 10-4

24. A ball is thrown vertically upward with a speed v. An identical second ball is thrown upward with a speed 2v (twice as fast). What is the ratio of the maximum height of the second ball to that of the first ball? (How many times higher does the second ball go than the first ball?)

a. 4:1

100. A plane is flying due South (270°) at 500 km/ h. A wind blows from East to West (180°) at 45.0 km/ h. Find the plane's velocity with respect to the ground.

a. 502 km/ h at 265°

78. A plane is flying due South (270°) at 500 km/ h. A wind blows from East to West (180°) at 45.0 km/ h. Find the plane's velocity with respect to the ground.

a. 502 km/ h at 265°

62. A soccer ball is kicked with a velocity of 25 m/ s at an angle of 45° above the horizontal. What is the vertical component of its acceleration as it travels along its trajectory?

a. 9.80 m/ s2 downward

57. Which of the following is an accurate statement?

a. A vector cannot have zero magnitude if one of its components is not zero.

23. Suppose a skydiver jumps from a high-flying plane. What is her acceleration when she she reaches terminal velocity?

a. It is essentially zero.

17. When an object is released from rest and falls in the absence of friction, which of the following is true concerning its motion?

a. Its acceleration is constant.

6. Suppose that a car traveling to the West (-x direction) begins to slow down as it approaches a traffic light. Make a statement concerning its acceleration.

a. The car is decelerating, and its acceleration is positive.

56. Which of the following operations will not change a vector?

a. Translate it parallel to itself.

31. An object is moving with constant non-zero velocity in the +x axis. The velocity versus time graph of this object

a. a horizontal straight line.

25. Ball A is dropped from the top of a building. One second later, ball B is dropped from the same building. As time progresses, the distance between them

a. increases.

61. Ignoring air resistance, the horizontal component of a projectile's acceleration

a. is zero.

45. The metric prefix for one one-thousandth is

a. milli.

39. If the velocity versus time graph of an object is a horizontal line, the object is

a. moving with constant non-zero speed.

8. If the velocity of an object is zero, does it mean that the acceleration is zero? Support your ANS with an example.

a. no, and an example would be an object starting from rest

41. A useful method of expressing very small or very large numbers is

a. scientific notation.

90. Two vectors and have components (0, 1) and (-1, 3), respectively. What are the components of the sum of these two vectors?

b. (-1, 4)

48. What is the conversion factor between km/ h and m/ s?

b. 0.278 m/ s

85. A swimmer heading directly across a river 200 m wide reaches the opposite bank in 6 min 40 s. She is swept downstream 480 m. What is the speed of the current?

b. 1.2 m/ s

79. An airplane with a speed of 120 km/ h is headed 30.0° east of north in a wind blowing due west at 30.0 km/ h. What is the speed of the plane relative to the ground?

b. 110 km/ h

98. A rifle bullet is fired at an angle of 30° below the horizontal with an initial velocity of 800 m/ s from the top of a cliff 80 m high. How far from the base of the cliff does it strike the level ground below?

b. 140 m

86. If a ball is thrown with a velocity of 25 m/ s at an angle of 37° above the horizontal, what is the vertical component of the velocity?

b. 15 m/ s

83. The driver of a motorboat that can move at 10 m/ s in still water wishes to travel directly across a narrow strait in which the current flows at 5.0 m/ s. At what angle upstream should the driver head the boat?

b. 30°

97. A projectile is launched with an initial velocity of 60.0 m/ s at an angle of 30.0° above the horizontal. What is the maximum height reached by the projectile?

b. 46 m

68. A ball is thrown at an original speed of 8.0 m/ s at an angle of 35° above the horizontal. What is the speed of the ball when it returns to the same horizontal level?

b. 8.0 m/ s

10. Suppose that an object is moving with constant acceleration. Make a statement concerning its motion with respect to time.

b. In equal times its velocity changes by equal amounts.

69. When a football in a field goal attempt reaches its maximum height, how does its speed compare to its initial speed?

b. It is less than its initial speed.

22. Suppose a ball is thrown downward in the absence of air resistance. Make a statement concerning its acceleration.

b. Its acceleration is constant.

18. Suppose a ball is thrown straight up. Make a statement about the velocity and the acceleration when the ball reaches the highest point.

b. Its velocity is zero and its acceleration is not zero.

20. Suppose a ball is thrown straight up, reaches a maximum height, then falls to its initial height. Make a statement about the direction of the velocity and acceleration as the ball is going up.

b. Its velocity points upward and its acceleration points downward.

13. Under what condition is average velocity equal to the average of the object's initial and final velocity?

b. The acceleration must be constant.

5. Suppose that a car traveling to the East (+x direction) begins to slow down as it approaches a traffic light. Make a statement concerning its acceleration.

b. The car is decelerating, and its acceleration is negative.

73. 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

b. be over the bomb.

46. The metric prefix for one one-hundredth is

b. centi.

59. 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

b. could be as small as 2.0 m, or as large as 12 m.

40. If the velocity versus time graph of an object is a straight line making an angle of 30 degrees with the time axis, the object is

b. moving with constant non-zero acceleration.

26. Ball A is dropped from the top of a building. One second later, ball B is dropped from the same building. As time progresses, the difference in their speeds

b. remains constant.

14. Objects A and B both start at rest. They both accelerate at the same rate. However, object A accelerates for twice the time as object B. What is the final speed of object A compared to that of object B?

b. twice as fast

55. Which one of the following is an example of a vector quantity?

b. velocity

33. The slope of a position versus time graph gives

b. velocity.

35. The area under a curve in an acceleration versus time graph gives

b. velocity.

52. How many grams is forty milligrams?

c. 0.0 40 g

95. A jumper in the long-jump goes into the jump with a speed of 12 m/ s at an angle of 20° above the horizontal. How long is the jumper in the air before returning to the Earth?

c. 0.84 s

82. The driver of a motorboat that can move at 10 m/ s in still water wishes to travel directly across a river 1.6 km wide in which the current flows at 5.0 m/ s. How long will it take to cross the river?

c. 2.4 min

49. A rectangular garden measures 15 m long and 13.7 m wide. What is the length of a diagonal from one corner of the garden to the other?

c. 20 m

77. A plane has an air speed of 200 m/ s due North, and is in a wind of 50.0 m/ s to the West. The plane's speed relative to the ground is

c. 206 m/ s.

99. A plane has an air speed of 200 m/ s due North, and is in a wind of 50.0 m/ s to the West. The plane's speed relative to the ground is

c. 206 m/ s.

91. A car travels 20 km west, then 20 km south. What is the magnitude of its displacement?

c. 28 km

65. At what angle should a water-gun be aimed in order for the water to land with the greatest horizontal range?

c. 45°

88. A butterfly moves with a speed of 12.0 m/ s. The x component of its velocity is 8.00 m/ s. The angle between the direction of its motion and the x axis must be

c. 48.2°.

74. 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

c. 6 times as far.