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South Pasadena  A.P. Physics
Chapter 4
Name________________________________
Newton’s Laws  Practice Test
d) 9.8 x the inertia
True/False
T 1. Aristotle believed that the natural state of a
body was at rest and that a force was necessary
to keep a body in motion.
T 2. Aristotle also believed that it was “natural” for
heavy things to fall and light things to rise.
13. If a steel ball is rolled alongside a circular
tubing on a flat table, what path would the
steel ball take after leaving the boundary of
the circular tubing? Draw the path that it
would take!
T 3. Galileo was concerned about how things
move, while Newton was concerned about why
things moved.
O
4. Galileo also believed like Aristotle that “a
force” is needed keep an object moving.
T 5. Frictional force is proportional to a normal
force acting on an object.
14. The weight of a 2 kilogram object
in Newtons is?
~ 20 N (19.6 N)
Matching:
15. The mass of an object whose weight is
9.8 Newtons is? 1 kg
F
Use either Galileo Galilei (G) or
Isaac Newton (N)
N 6.
Studied Dynamics
N 7.
Lived 1642-1727.
G 8.
Lived 1564-1642.
G 9.
Studied Kinematics
___10. You are in outer space and you throw the
2 kilogram mass away from your
spacecraft; describe the motion of the object
and your motion.
2 kg mass moves away from you and you move
in opposite direction with smaller acceleration
___11. If you are standing on a moving bus and you
drop a coin to the floor, how will the coin fall,
a) relative to the bus and b) relative to the
ground outside?
a) straight down vertically
16.
Does a 2-kilogram bunch of bananas, have twice
the weight, as a 1-kg bunch of bananas when
weighed in the same location? YES
Fill in the missing information:
17.
Mass is a measure of the amount of
Matter in an object.
18.
Volume is the amount of SPACE that an
object occupies.
19.
Weight is a measure of the amount of
FORCE DUE TO GRAVITY on an object.
20. An object has a weight of 4.5 N and is sitting on a
table. What is the value for the normal force?
─ 4.5 N
Its direction is pointing
UP
b) forward in parabolic path
___12. A 4 kilogram mass has how much inertia
compared to a 2 kilogram object?
a) 2x the inertia
21. If you have a mass of 60 kilograms and a weight
of 120 pounds on the Earth, what will be your
mass and weight on the moon (where gravity is 6
times less than on Earth?
Mass on Moon =
60 kg
b) ½ the inertia
c) 1/9.8 the inertia
Weight on Moon =
1/6 x 120 = 20 lbs
22. If an object is 2.0 N on the earth (Object A) and
another object is 2.0 N on the moon (Object B),
which one has a greater mass?
a) Object A
b) Object B
a = 2.0 N / 4.0 kg = 0.50 m/s2
23. Which object has greater weight on the earth?
a) Object A
30. An object has a mass of 4.0 kg and is pulled in
opposite directions with forces of 3.0 N & 5.0 N.
What is the object’s acceleration?
b) Object B
31. 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 is the acceleration of the cart?
a = (8.0 N – 2.0 N) / 2.0 kg = 3.0 m/s2
24.
Fill in the correct values for the Net Force for
the following three pairs of forces:
5 N East and 10 N East
Net Force
=?
15 N East
5 N West and 10 N East
5 N East
5 N East and 5 N West
Zero
9.4 N So.
East
Applied Forces
5 N East and 8 N South
25. A girl whose weight is 200 N hangs from a bar
supported by two strands of rope. What is the
tension in each strand of rope?
a) 400 N
b) 300 N
32. If an object has a mass of 5.0 kg and it is
accelerating with at 3.0 m/s2, while
someone is pushing on it with a force of 19
t is the force of friction acting on
Newtons, what
the object?
F x 3.0 m/s2 = 15 N
Fnet = 5.0 kg
Fnet = 19 N + Ff = 15 N
________
Ff = ─ 4.0 N
33. An object of mass 2.5 kg is sliding on a surface
with an applied force of 8.0 Newtons acting on it.
If the force of friction acting is 6.5 Newtons, what
would be the acceleration of the object?
a = Fnet/m = (8.0 N – 6.5 N)/ 2.5 kg = 0.60 m/s2
c) 200 N
d) 100 N
26. An object that is moving, must have at least ___
force(s) acting on it.
ONE
27. The acceleration of an object is inversely
proportional to the MASS
34. For the problem above, what would be the object’s
acceleration if there were an additional force of
10.0 N, pushing on the object?
18 N – 6.5 N = 2.5 kg (a)
a = 4.6 m/s2
28. The speed of an object dropped in air will continue
to increase without limit until it strikes the
ground. Explain why this statement is true or
why it is false.
It is false. When force of air resistance equals
the weight of object, it continues to move at
constant velocity This is called terminal
velocity.
29. If a net force of 24 Newtons is accelerating a mass
at 4.0 m/s2, what is the value of the mass?
m = F/a = 24 N/4.0 m/s2 = 6.0 kg
35. 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 . . .
a) The air molecules outside the balloon pushing
back on the rubber balloon.
b) The air molecules inside the balloon pushing
back on the balloon.
c) The rubber balloon pushing on the air
molecules outside the balloon.
(Here is a question from Regular Conceptual Physics)
36. The force of air resistance acting on an elephant,
compared to the force of air resistance acting on
a feather is . .
42. 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 . ?
a) greater for the elephant
a) greater than the force exerted by the son
b) greater for the feather
b) less than the force exerted by the son
c) the same for both the elephant and feather.
c) equal to the force exerted by the son
37. The reason the two objects above have
the same value for their accelerations in a
vacuum is because . .
43. If the father has a mass of 80 kg and the son has a
mass of 40 kg, how will their accelerations
compare?
a) as mass increases, the force of gravity
acting increases proportionally by the
same amount.
a) The acceleration of the father will be twice as
great.
b) as mass increases, the force of gravity
acting decreases proportionally by the
same amount.
b) The acceleration of the son will be twice as
great.
c) their accelerations are the same in a
vacuum only if their masses are identical.
c) They will both have the same acceleration.
R
from the ground.
38. Draw a free body diagram (to the right of the
question) for an 85 kg skydiver is accelerating
through the air, with a force of air resistance
of 250 N acting on the skydiver.
●
39. What is the acceleration of the skydiver?
W
a = [(85 kg) ( 9.8 m/s2)] ─ 250 N = 6.9 m/s2
85 kg
40. Another skydiver of mass 70 kg, is moving
through the air with an acceleration of 5.0 m/s2
What is the force of air resistance acting on
her as she falls?
W = mg = ─ 686 N
─ 686 N + R = (70 kg) ─5.0 m/s2 = ─350 N
R = ─ 686 N + 350 N = 336 N
41. When the force of air resistance acting on a
skydiver is equal to the skydiver’s weight, what
will be the motion of the skydiver?
a) He will stop moving and be at rest because
the net force is zero.
b) He will continue to move but with a constant
velocity.
c) He will continue to accelerate.
d) He will start moving upward, away
44. Consider a horse pulling a carriage along the
road by exerting a force on the carriage.
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.
45. The force that a bug exerts on the windshield of
a moving car, compared to the force that the
windshield exerts on the bug is?
a) much greater
b) much less
c) exactly equal
(Textbook question #10)
46. 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. If you
want the bottom string to break when you pull
on it, should you pull the bottom string
m2
m1
Two masses are hanging over an Atwood pulley.
One has a mass of 235.0 grams (0.235 kg) and the
other mass has a mass of 238.0 grams (0.238 kg).
49. What is the net force (in Newtons) causing the
system of masses to accelerate?
(0.238 kg ─0.235 kg)x 9.8 m/s2 = 0.0294 N
a) slowly
b) with a sudden jerk (inertia!)
47. (From the inertia activity stations) When a cork is
tied to a string in a flask of water and the flask is
quickly accelerated to the right, while the flask is
upside down, the motion of the cork will be
a) to the right, also
b) to the left
48. A spring scale is suspended horizontally between
two equal weights of 10 Newtons, each hanging
over a pulley and hanging downward over the two
ends of the table.
10
10
Would the spring scale read 0, 10, or 20 Newtons,
or something else?
10 Newtons
50. What would be the acceleration of the two
masses?
a = 0.0294 N /(0.238 kg + 0.235 kg)
= 0.0622 m/s2
51. If the masses moved a distance of 85.0 cm in
an average time of 4.7 seconds, what would the
acceleration of the two masses be using the
formula d = ½ at2?
a= 2 x 0.850 m = 0.077 m/s2
(4.7 s)2
52. Which formula gave the higher acceleration?
a) F= ma
b) d = ½ at2
The Situation
Mr. Nicholls has asked for two volunteers from the
class to help with a demonstration. He has Frank and
Beth sit opposite each other on two chairs with wheels.
Beth takes off her shoes and puts her feet against
Frank’s knees. Beth pushes off, and the two chairs
move in opposite directions. Beth is quite a bit smaller
than Frank, so her chair moves noticeably faster than
his.
“Which student, Frank or Beth, experiences the
greater force?”, Mr. Nicholls asked.
Do you have an answer to Mr. Nicholls’ question?
The Prediction
Here were the class’s responses.
Mary:
“Beth did the pushing and Frank was
just sitting there, so Beth must have
been pushing harder that Frank
because she was causing the
acceleration.”
Cathy:
“I agree with Mary. Besides, she was
moving faster than Frank. Her
acceleration was larger, so she must
have experienced the greater force.”
Daniel:
“I disagree. Frank didn’t accelerate
as much as Beth because he has a
greater mass. A greater mass
requires a greater force, so Frank
must have experienced a greater
force than Beth.”
Which student do you agree with? Or do you have a
different answer or explanation?
The Answer
“Wait a minute,” says John, “I think this is one of
Nicholls’ trick questions. The first law says forces
cause accelerations, which we saw for ourselves. And
the second law says force, mass and acceleration are all
related, which is what we have been talking about. But
what about the third law?”
“John is right,” says Mr. Nicholls. “All of your
arguments make a lot of sense, but in fact the two
forces are equal in magnitude and opposite in direction
because of Newton’s Third Law of Motion.”
So then what is wrong with each of the explanations
given by Mary, Cathy, and Daniel? How can we
reconcile their observations with Newton’s Third Law
of Motion?”