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South Pasadena  Physics
Mid Term 
Name____________________ Period___
Practice Test ANSWERS
1About
True/False
True
Science
1. Physics is the most basic of all the sciences.
False
2. Science deals with practical problems while technology deals with theoretical questions.
True
3. Theories must always be modified as new evidence is gathered.
True
4. Scientific Claims made by scientists must be able to be proven wrong.
Matching:
5. Theory
c
(a) A statement that is not immutable or is absolute.
6. Hypothesis
d
(b) Something that envelops the overriding idea dealing with phenomena.
7. Fact
a
(c) Based on a synthesis of a large body of information.
8. Concept
b
(d) An educated guess regarding the behavior of some phenomenon.
9. Convert the number 70 years into seconds and express the answer as a power of 10.
70 years x 365 days/yr x 24 hours/day x 3600 seconds/hour = 2 x 10 9 s
10. How many significant figures does the number 15.00 have?
4
11. Forty kilometers is equivalent to how many meters? 40 km x 1000 m/km
=
40,000 m
12. Fifty milligrams is how many micrograms? 50 mg x 1000 μg/ mg = 50,000 μg
13. What is the product of 13.95 cm and 2.83 cm?
a) 39
b) 39.5
c) 39.48
(No questions like this on midterm exam)
14.
2
Fill in the missing information:
Speed (km/hr)
68
95
15.

Linear
d) 39.47
Motion
Distance (km)
Time (hours)
350
5.15
3.3
.035
A car starting from rest moves with constant acceleration of 2.0 m/s2 for 10 s, then travels with constant speed
for another 10 s, and then finally slows to a stop with constant acceleration of – 2.0 m/s2. How far does it
travel?
400 m
d1 = ½ (2.0 m/s2)(10 s)2 = 100 m
16.
d2
vf = 2.0 m/s2 (10 s) = 20 m/s, then d2 = 20 m/s x 10 sec. = 200 m
d3
time = (vf – vi)/a = (0 – 20 m/s)/-2.0 m/s2 = 10 sec. d1 = ½ (-2.0 m/s2)(10 s)2 = 100 m
total distance is 100 m + 200 m + 100 m = 400 m
If you try to catch a ruler to measure your reaction time and the ruler falls 5.0 cm, what is your reaction time?
time of fall = √2d/g = √2(0.05 m)/g = 0.10 seconds
17. An apple is thrown upward into the air with an initial speed of 30 m/s.
a) How fast is it going after 2.0 seconds?
b) What is its acceleration after 3.0 seconds?
vf = vi +gt
10.4 or 10 m/s
acceleration is always =
c) What is the initial velocity of the apple when it is thrown upward?
18. If you drop the apple from the balcony of a tall building,
how far will if travel in 3.0 seconds?
d = ½ (9.8 m/s2) (3.0 sec)2 =
19. When a car is turning a corner, is it accelerating?
-9.8 m/s2
+ 30 m/s
44 m
yes, because it is changing direction
20. Sketch a distance vs. time graph and a speed vs. time graph for ball being dropped off the science balcony.
|
|
|
|
| curved lined sloping upwards
|_____________________
time
|
|
|
|
|
|____________________
time
21. Describe in words, the motion of the falling ball in terms of distance and speed and acceleration over time:
The distance increases by increasing amounts each second. The speed increases by constant amounts each
second. The acceleration stays constant at – 9.8 or −10 m/s2 each second.
3

Projectile
Motion
22. Label the following as either Vector quantities or Scalar quantities.
Treasure map V
Velocity V
Your shoe size S
Speed
S
Your weight
V
Force
V
Acceleration
V
S.S #
S
23. What is the resultant of two vectors, X & Y at right angles to each other, whose magnitudes
are 60 km/hr and 80 km/hr? Sketch the vector diagram
Use the pythagorean theorem
100 km/hr
24. A projectile is launched horizontally from the science balcony with an initial horizontal velocity
of 15 m/s. The height of the balcony is 6.0 meters high. How far away horizontally does the
projectile land?
17 m
time of fall = √2d/g = √2(6.0 m)/9.8 = 1.11 sec
distance = 15 m/s x 1.11 seconds = 17 m
25. If a blow dart is shot thru a blow dart gun and travels 12.0 meters away and falls a vertical
distance of 4.0 centimeters. What was the initial velocityof the dart in meters/second?
133 m/s
time of fall = √2d/g = √2(0.04 m)/9.8 = 0.090 sec
velocity = 12.0 meters/0.090 seconds = 133 m/s
26. What is the acceleration of the dart in the horizontal direction?
Gravity only acts in the vertical direction.
zero
-9.8 m/s2
27. What is the acceleration of the dart in the vertical direction?
28. If the blow dart was shot upward at an angle of 35° at what other angle could
the dart be shot so that it would travel the same horizontal distance?
55°
Complementary angles of fired projectiles travel the same horizontal distance.
29. A bullet is fired horizontally across a field, from a gun, while another identical bullet is dropped
to the ground from the same height as the gun, at the instant the bullet is fired. Do both bullets
hit the ground at the same time? Why or Why not?
Both bullets hit the ground at the same time because the same force of gravity is
acting on both of them, causing them to both fall at the same rate. The fired bullet
will of course also travel a farther distance than the dropped bullet.
4Newton’s
1
s t
Law
of
Motion-Inertia
30. Which has greater inertia: a 2 kilogram mass or a 4 kilogram mass?
4 kg
31. You are in outer space and you throw the 2 kilogram mass away
from your spacecraft; describe the motion of the object.
It will travel in a constant direction and with a constant speed.
Law of INERTIA
32. What is the weight of the 2 kilogram object in Newtons?
Weight = mg = 2 kg (9.8 m/s2) = 19.6 N
33. If you have a mass of 60 kilograms and a weight of 120 pounds, what will your
mass and weight be on the moon?
Mass is the same everywhere in the universe, but your weight would be
6 times smaller on the moon.
60 kg
and 20 pounds
34. If an object is 2.0 N on the earth and another object is 2.0 N on the moon,
which one has a greater mass?
The 2.0 Newton object on the moon, since gravity is smaller on the moon, it requires a greater mass to be
equivalent in weight to the less massive object on the Earth.
m = W/g
Earth m = W/
g
Moon
m = W/
g
35. A heavy mass is attached to a string and hung from a horizontal bar and then a second string
is attached to the lower end of the mass and is dangling below the mass. The mass has inertia.
If you want the bottom string to break when you pull on it, should
you pull the string slowly or with a sudden jerk?
sudden jerk to take advantage of the inertia of the heavy mass
36. If you wanted to easily pass a sharp knife thru a raw potato, should you . . (a)
a) place knife vertically on table, place potato on top and then pound bottom of knife to table or
b) place potato on table and jab the knife through the potato
37. If you are standing on a moving bus and you drop a coin to the floor, how will the coin fall?
a) It will fall directly down in a straight line to your feet, because of the coin’s inertia.
(a)
b) It will fall to the ground farther away from your body than where it started, because of inertia.
5
Newton’s
2
n d
Law-
Force
&
Acceleration
38. If a 4.0 kilogram mass is accelerated at a rate of 3.0 m/s2, what net force must be causing the acceleration?
F net = ma
= 4.0 kg (3.0 m/s2)
=
12 N
39. If a net force of 24 Newtons is accelerating a mass at 4.0 m/s2, what is the value of the mass?
mass = Fnet/acceleration
=
24 N/4.0 m/s2
=
6 kg
40. If a 2.0 kg cart is being pulled with a force of 8.0 Newtons against a frictional force of
2.0 Newtons, what the acceleration of the cart?
a = Fnet/ mass =
(8.0 N – 2.0 N)/2.0 kg =
3.0 m/s2
41. An 85 kg skydiver is accelerating through the air, which is exerting 250 Newtons of air resistance.
What is the acceleration of the skydiver?
Weight = mg = 85 kg (9.8 m/s2) = 833 N
a = net force/mass = (833 N - 250 N)/85 kg =
6.9 m/s2
42. The force of gravity acting on an elephant, compared to the force of gravity acting on a feather is
a)
b)
c)
(a)
greater for the elephant because the elephant has more mass W = mg
greater for the feather
the two are equal since the acceleration of the two is the same
43. The reason the two objects above have the same value for their accelerations in a vacuum is because . . (a)
a)
b)
c)
as mass increases, the force of gravity acting increases proportionally the same amount.
as mass increases, the force of gravity acting decreases proportionally the same amount.
their accelerations are the same in a vacuum only if their masses are identical.
6
Newton’s
3
r d
Law
of
Motion-Action
&
Reaction
44. If a father and young son are on a frictionless ice pond with a rope between them and they both pull
on the ends of the rope, the amount of force exerted by the father on the son will be . . ?
(c)
a) greater than the force exerted by the son
b) less than the force exerted by the son
c) equal to the force exerted by the son
45. If the father has a mass of 80 kg and the son has a mass of 40 kg, how will their accelerations compare? (b)
a) The acceleration of the father will be twice as great
b) The acceleration of the son will be twice as great
c) They will both have the same acceleration
46. When a balloon filled with air is released through the air, it will fly all over the place. If the action
force is the rubber balloon pushing on the molecules of air in the balloon, then the reaction force is . . . (b)
a) The air molecules outside the balloon pushing back on the rubber balloon.
b) The air molecules inside the balloon pushing on the balloon.
c) The rubber balloon pushing on the air molecules outside the balloon.
47. Consider a horse pulling a carriage along the road by exerting a force on the carriage.
(d)
a) The reaction force acting on the horse cancels the action force by the horse.
b) The reaction force acting on the horse is opposite in direction but not equal
in magnitude to the action force by the horse.
c) The reaction force is acting on the same object as the action force.
d) The reaction force is acting on a different object and is equal in magnitude to the action force.
48. When a bug smashes into a windshield on a moving car, the car must be affected in speed by the bug,
according to Newton’s Third Law of Motion?
True
49. A spring scale is suspended horizontally between two equal weights of 50 Newtons, each hanging over a
pulley and hanging downward over the two ends of the table. The reading on the scale must be . . .
a) 0 Newtons
b) 50 Newtons
c) 100 Newtons
(b) 50 Newtons
7

Momentum
50. Which object has a greater momentum? A 1200 kg car moving at 10 miles per hour or
an 800 kg car moving at 25 miles per hour?
800 kg car
momentum p = mv
51. If the momentum of a soccer ball is 12 N-s and it is moving at 6.0 m/s, what is the mass of the soccer ball?
m = p/v = 12 N-s/ 6.0 m/s
=
2 kg
52. A 55 kg person jumps off a chair and is moving at 3.0 m/s before making contact with the floor.
How much impulse did the floor exert on the person if the person required 1.0 second to come to rest?
Impulse = F x t = m (vf – vi) = 55 kg (0 – 3.0 m/s) = - 165 N-s
53. How much force in Newtons did the person experience in coming to rest?
F = impulse/time = -165 N/1.0 second =
- 165 N
54. If the person had come to rest in 0.01 seconds by landing with stiff legs, how much force
would the person experience on the landing?
100 x more force (1 second/0.01 second) = 100 x (– 165 N) = - 16,500 N
55. An inelastic collision occurs between two automobiles, “a” and “b” whose masses are 1200 kg and 800 kg
respectively. If car “a” had been moving at 40 m/s and car “b” was at rest, what is the velocity of the two
entangled cars after collision?
mv + 0 = (m1 + m2) v’
v’ = (1200 kg)(40 m/s)
(1200 kg + 800 kg)
=
24 m/s
56. If car “b” had been moving towards car “a” at 25 m/s, what would be the velocity of the two cars after collision?
v’ = [(1200 kg)(40 m/s)] + [(800 kg) (-25 m/s)] =
(1200 kg + 800 kg)
14 m/s
57. At a fireworks display, a firework has a momentum of 25 N-s when moving northward into the air before it
explodes. After the explosion, two of the three pieces are moving southward with a combined
momentum of 15 N-s. What is the momentum of the third piece?
25 N-s North = 15 N-s South + X
8

X = 40 N-s North
Energy
58. If you turn on the radio in your car with the engine off, will more gasoline be burned later
when the car engine is turned on, as a result of having turned on the radio? YES NO.
Law of Conservation of Energy (Energy cannot be created or destroyed!)
59. If you do 8.0 joules of work in lifting your 2.0 kg physics book, how high in centimeters did you lift your book?
Work = F x d = mg x h
so, h = 8.0 J/(2.0 kg) 9.8 m/s2) = 0.408 m
= 41 cm
60. If you lifted your book by expending 16.0 watts of power, how many seconds was required to lift the book?
Power = Work / time or time = 8.0 joules/ 16 watts = 0.5 s
61. How many joules of potential energy does your 2.0 kg physics book have while sitting on your desk
which is 80 centimeters above the ground?
P.E. = mgh = (2.0 kg) (9.8 m/s2) (0.80 m)
=
15.7 or 16 Joules
62. If your physics book fell off of your desk, what velocity would it have before hitting the floor?
v = √(2 gh = 3.96 or 4.0 m/s
(or you can use K.E. = ½ m v2 and then say that the kinetic energy is equal
to the potential energy and then solve for v)
63. A bowling ball hanging from the ceiling is brought back to a point where it has 85 joules of potential energy.
After being released, it has 25 joules of potential energy at a certain point. How many joules of kinetic energy
does it have at this point?
85 Joules – 25 Joules = 60 Joules
64. A lever is used to lift an 80 Newton object to a height of 1.0 m. If you exerted an input force of 20 Newtons,
through how much distance did you move the lever?
F x d = F x d or d in = 80 N x 1.0 m = 4.0 m
20 N
65. What is the mechanical advantage of this lever?
M.A. = 80 N / 20 N = 4.0
66. How much work must be done to stop a 1000-kg car traveling at 31 m/s?
Work done = ΔK.E. = 0 – ½ 1000 kg (31 m/s) 2 =
- 480,500 J
67. An oxygen molecule of mass 5.31 x 10-26 kg has a kinetic energy of 6.21 x 10-21 Joules. How fast is it moving?
K.E. = ½ mv2 or v = √(2 K.E.)/m =
9

Circular
484 m/s
Motion
68. A bug is crawling on the record of a record player near the axis of rotation.
An ant is also crawling near the outer edge of the record. If the record player is turned on,
which one experiences a greater linear velocity?
the ant
Which one is experiencing the greater angular velocity?
neither
69. If the bug is at a radius of 2.0 cm (0.020 m) from the axis of rotation, and the period of rotation
of the record (time for one rotation) is 2.0 seconds, what is the linear velocity of the bug?
0.063 m/s
v = 2πr/T = 2 x 3.1415 x 0.020 m/ 2.0 seconds =
70. If the bug has a mass of 15 grams (0.015 kg) and is at a radius of 2.0 cm (0.020 m) from the axis
of rotation, what is the centripetal acceleration of the bug?
0.197 m/s2
ac = v2/r = (0.063 m/s)2/0.020 m =
71. What centripetal force (in Newtons) is acting on the bug as it is rotating?
0.00296 N
Fc = m ac = 0.015 kg (0.197 m/s2) =
72. When you are a passenger in a car and the car is turning right on a turn, in which direction do you feel
being pulled or pushed?
Left
73. Is this push or pull that you feel, a centripetal or centrifugal force?
centrifugal
74. Explain to your partner, what is the cause of the force that you feel on the turn!
Your body wants to go straight because of its inertia and the car is turning right into your body.
75.
What is the gravitational force of attraction between the Earth and the moon, whose masses
are 5.97 x 10 24 kg and 7.35 x 10 22 kg, respectively and the distance between the Earth
and the moon is 3.84 10 8 m? The universal gravitational constant, G, is 6.67 x 10 –11 N-m2/kg2.
F = G (m1m2)/d2 = (6.67 x 10 –11 N-m2/kg2) (5.97 x 10 24 kg) (7.35 x 10 22 kg) = 1.98 x 10 20 N
(3.84 10 8 m)2