## kaylalynn one year ago Final exam review help?!?!

1. kaylalynn

I have 3 study sheets.

2. kaylalynn

3. kaylalynn

for # 1 i got 34km/h

4. Coolsector

no, you have to multiply by 3.6

5. kaylalynn

why?

6. Coolsector

|dw:1383926098747:dw|

7. kaylalynn

4.9 m change it to km it is 0.0049km/s * 60 *60 = 33.8

8. Coolsector

4.9 m change it to km it is 0.0049km this is correct. but then when you change seconds into hours you divide by 3600 since you divide it in the denominator it is like multiplying by 3600 so eventually 0.0049 * 3600 = 17.64 km/h

9. Coolsector

look at my draw

10. Coolsector

-> 0.0049km/s * 60 *60 = 33.8 it is 17.64 and not 33.8

11. Coolsector

0.0049 * 60 * 60 = 17.64

12. Coolsector

maybe you did mistake when you enter the numbers into the calculator

13. kaylalynn

the options are 94,000 km/h 34 km/h 2.6 km/h 34,000,000 km/h

14. Coolsector

well what can i say : http://www.unitconversion.org/velocity/meters-per-second-to-kilometers-per-hour-conversion.html you may check yourself here

15. Coolsector

0.0049 * 60 * 60 = 17.64 do it in the calculator and see

16. Coolsector

m is for meters right ? :O

17. kaylalynn

yes. Idk maybe the options are wrong. i keep getting 17.64 too.

18. Coolsector

i guess they are wrong

19. kaylalynn

A physical quantity X depends on mass, distance, and time. Use dimensional analysis to decide which of these is a possible expression for X where a is acceleration, v is velocity, and F is force. It's either X=Ft or X=1/2at^2 right?

20. Coolsector

well in x=1/2at^2 there is no mass

21. kaylalynn

would X=Ft work?

22. Coolsector

you have options ?

23. kaylalynn

yes X=Ft X=at X=vt and X=1/2at^2

24. Coolsector

yes Ft is the one

25. kaylalynn

for 3 I want to say B?

26. Coolsector

no

27. Coolsector

(just to make sure that you understand Ft units are [kg m / s] so it has mass distance and time)

28. Coolsector

now for 3. think what happens to y when x is small and when x is big..

29. kaylalynn

im confused

30. Coolsector

y = k/x for low values of x like when x goes to zero y will be very large for high values of x like when x goes to infinity y will be very low agree ?

31. kaylalynn

yes so thus my answer is A? AS X gets larger Y gets smaller.

32. Coolsector

yes ! A

33. kaylalynn

A balloon is expanded to the same volume as that of a human head. Do an order-of-magnitude estimate of the volume of this balloon in cm3

34. kaylalynn

1,000 cm3?

35. Coolsector

i think it iscorrect

36. kaylalynn

Which equation represents inverse proportionality? y=mx?

37. Coolsector

y=mx is linear proportionality direct ..

38. kaylalynn

y=mx y=mx^2 +b for nonzero b y=m/x y=mx^2

39. Coolsector

we had one like this before .. we want inverse so when one is high the other is low and when one is low the other is high ...

40. kaylalynn

so how would that be represented by an equation?

41. Coolsector

y=m/x as i said we had something like this before when we chose graph A

42. kaylalynn

oh. okay so its like the graph.

43. kaylalynn

A bicycle and rider travel along a road. Which of the following statements is true?

44. kaylalynn

The bicycle wheels rotate and translate the entire bike and the rider.

45. Coolsector

please write the other options as well

46. kaylalynn

Only the bicycle rider undergoes a translation. The bicycle wheels rotate and translate the entire bike and the rider. Only the bicycle undergoes a translation. Neither the bicycle nor the rider undergoes a translation.

47. Coolsector

48. kaylalynn

Suppose you are on a conveyor belt walkway at an airport. The walkway is moving at 0.50 m/s. You walk backward at 0.80 m/s to hand your suitcase to a friend who is 3.0 m behind you. A security guard stands alongside the walkway watching this. What is your speed relative to the guard? im not sure how to do this one.

49. Coolsector

so if you were not moving the relative speed was 0.5m/s correct?

50. kaylalynn

correct

51. Coolsector

now i guess the 0.8m/s walking backwards is relative to the belt! so we have: 0.5 - 0.8

52. Coolsector

do you understand why ?

53. kaylalynn

because he is walking backwards at 0.8

54. Coolsector

yes. not moving on the belt : 0.5 moving forward on the belt at x : 0.5 + x moving backward on the belt at x: 0.5 -x

55. kaylalynn

okay

56. kaylalynn

An airplane travels southwest a distance of 650 km at a velocity of 430 km/h. How long does the trip take in hours? 1.5?

57. Coolsector

correct

58. Coolsector

(650/430 = 1.5116...)

59. kaylalynn

On the position-time graph, what is the average velocity between 5 s and 10 s?

60. kaylalynn

61. kaylalynn

62. Coolsector

average velocity = (y2-y1) / (t2 -t1)

63. Coolsector

between two points : (t1,y1) and (t2,y2)

64. kaylalynn

4m/s?

65. Coolsector

at 5 sec the height is 10 so (5,10) and at 10 sec the height is 30 so (10,30) (30-10) / (10-5) = 4 correct

66. kaylalynn

A ball is dropped from a tower. It strikes the ground with a speed of +19.0 m/s. How high is the tower? 18.4m

67. Coolsector

you take the value of g as 9.8 ?

68. Coolsector

so yes correct..

69. Coolsector

v=gt so t=v/g now plug it into h = 0.5gt^2 = 0.5v^2/g = 18.4

70. kaylalynn

A ship travels south at 15 km/h for 4 h. What is the ship's displacement in km? 60km South?

71. Coolsector

correct 15*4 = 60

72. kaylalynn

A ball is rolling down a hill at +2.0 m/s. The ball is uniformly accelerating at +4.0 m/s2. What will the ball's velocity be 3.0 s later? 14m/s because v=u+at

73. kaylalynn

What additional force must be applied so that the block does not accelerate? 10N West?

74. kaylalynn

A 1,560 kg car is accelerating at 1.30 m/s2. What net force acts on the car? F=ma so 2028 rounds to 2030?

75. kaylalynn

Which statement is equivalent to Newton's first law? No net force acting on an object means no acceleration.

76. kaylalynn

A tension force of 2.50 N acts horizontally on a 2.00 kg block. The block accelerates at 0.750 m/s2. What is the force of kinetic friction? 1N?

77. kaylalynn

however the options are - 3.33 N - 1.50 N - 1.00 N - 4.00 N

78. Coolsector

ball - correct block - correct car - correct newtons first law - seems like it is correct but it is better to see the other options tension - it is -1 (remember that the kinetic friction force is against the direction of the motion) so you right about the magnitude but the sign is there to show what is the direction.

79. Coolsector

i guess that you solved it like 2.5 - Fk = ma and then you got Fk =1 but look at the equation - you already chose the direction with the minus sign.

80. kaylalynn

No net force acting on an object means no acceleration. For every action there is an equal and opposite reaction. Mass is directly proportional to weight. The acceleration of an object is the net force acting on it divided by its mass.

81. Coolsector

so it is right.

82. kaylalynn

The acceleration due to gravity on the surface of Mars is gmars = 3.7 m/s2. How much would an 11 kg bag of potatoes weigh on Mars? 41N?

83. Coolsector

yes

84. Coolsector

3.7*11

85. kaylalynn

The 48 kg student on skates pushes the 40 kg student on skates. The 40 kg student accelerates at 3.0 m/s2. What is the acceleration of the 48 kg student?

86. kaylalynn

87. Coolsector

newton's third law..

88. Coolsector

another hint ?

89. kaylalynn

F=ma?

90. Coolsector

newton's third says that if body A push body B with force F then body B push body A with the same force F in the opposite direction

91. kaylalynn

i feel stupid. sorry. ive been up all night

92. Coolsector

what is the force that acts on the 40kg student ?

93. Coolsector

94. kaylalynn

3m/s?

95. Coolsector

i asked about the force The 40 kg student accelerates at 3.0 m/s2 so the force on him is 40 * 3 = 120 N now according to newton's third law it is the force that acts on the second student as well (in the other direction) so 120 = 48 * a a = 120 / 48

96. kaylalynn

2.5 m/s

97. Coolsector

yes (well they might have there -2.5 since it is in the other direction)

98. kaylalynn

A 0.156 kg ice puck collides with a 0.170 kg ice puck. Both were originally moving at the same speed. Which one has the larger change in velocity?

99. kaylalynn

The 0.156 kg puck changes velocity the most. The 0.170 kg puck changes velocity the most. They both have the same change in velocity. They each have no change in velocity. I say it is the first one...

100. Coolsector

so the situation is that they are moving toward each other ? and then elastic collision ?

101. kaylalynn

i asume

102. Coolsector

correct then

103. kaylalynn

A diver jumps down on a springboard, bounces back up, and dives into the pool. Which of these is one of the action-reaction pairs involved?

104. kaylalynn

the force on the board as the diver bends it downward and the force on the diver as the board springs back up the force of the board on the diver as he moves down and the force of the board on the diver when pushed back up the springiness of the board in moving back up the force the diver exerts on the water and the force the water exerts on the diver

105. Coolsector

so what do you think ?

106. kaylalynn

A?

107. Coolsector

yes

108. Coolsector

newton's third law always involved two bodies

109. kaylalynn

A force of 100 N acts in a direction at an angle of 30° with the x-axis. What is the magnitude of the x component of the force?

110. kaylalynn

111. rajat97

|dw:1383940674800:dw| yes the accurate answer is 86.5 newton

112. kaylalynn

Two movers are pushing a large crate along the ground, one with a force of 30 N east and the other with a force of 40 N north. The crate does not move. What is the magnitude of the force of static friction?

113. rajat97

always remember for ease of resolving the forces into perpendicular directions, the component of force near the angle is the force x cos theta and the one which is away from it is f x sin theta

114. rajat97

|dw:1383940923978:dw| the forces are perpendicular so the resultant is $\sqrt{F1^{2}+F2^{2}}$ therefore the resultant is 50N and the force of friction is equal to it

115. kaylalynn

Which of these is true about an object thrown straight up in the absence of air resistance?

116. kaylalynn

Its acceleration is constant. The direction of its velocity is constant. Its acceleration and velocity are both momentarily zero at maximum height. Its acceleration increases as it falls.

117. Coolsector

so what do you think ?

118. kaylalynn

C?

119. Coolsector

well no does g change during the motion ?

120. kaylalynn

i want to say no

121. Coolsector

because the acceleration does not change

122. kaylalynn

so it would be A?

123. Coolsector

yes

124. Coolsector

note that at the maximum height the velocity is indeed zero. but what makes it go down ? the acceleration.

125. kaylalynn

The velocity of an object increases from 5.0 m/s to 15 m/s in 2.0 s. What is the average acceleration of the object?

126. ayhan

5m/sn2

127. ayhan

ok

128. rajat97

i'm on it average velocity is change in velocity in unit time so here it is 15-5/2 =5m/s^2

129. kaylalynn

is it + or -?

130. rajat97

change in velocity is final velocity -initial vel as final vel is greater than initial vel , it will be posotive

131. rajat97

and if vel is increasing, then acceleration is +ve

132. kaylalynn

What shape does a position vs. time graph have for an object in uniform acceleration?

133. kaylalynn

134. rajat97

i think its cubic as the degree of the equation increases as we move towards position time graph i mean to say its linear in v-t graph so it may be quadratic in x-t graph

135. ayhan

hi again

136. kaylalynn

okay and hi

137. rajat97

138. ayhan

ok.bye

139. rajat97

140. rajat97

somethings gotta go wrong with openstudy well i live in india and its 2:45 am and i think i shall sleep now but if you have any questions please post them i'm onine for 15 mins

141. kaylalynn

no, my mom needed help with something.

142. kaylalynn

A book is being pushed along a table at constant speed. The coefficient of static friction is 0.75, and the coefficient of kinetic friction is 0.30. The book has a mass of 0.50 kg. What is the force of friction?

143. kaylalynn

1.5N

144. Coolsector

correct