# Concept Development Physics Exam Practice: Physics Answers 2021

## Concept Development Physics Exam Practice: Physics Answers 2021

Question Title:

Concept Development Physics Exam Practice

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Name
Class
Date
Concept-Development
Practice Page
13-1
Inverse?Square Law
1. Paint spray travels radially away from the nozzle of the can in straight lines. Like gravity, the
strength (intensity) of the spray obeys an inverse-square law. Complete the diagram by ?lling
in the blank spaces.
9
16
1/9
1/16
2. A small light source located 1 m in front of an opening of area 1 m2 illuminates a wall behind. If the
wall is 1 m behind the opening (2 m from the light source), the illuminated area covers 4 m2. How
many square meters will be illuminated if the wall is
5 m from the source?
25 m2
10 m from the source?
100 m2
3. Hold your hands outstretched, one twice as far from your
eyes as the other, and make a casual judgment as to which
hand looks bigger. Most people see them to be about the
same size, while many see the nearer hand as slightly
bigger. Almost nobody upon casual inspection sees the
nearer hand as four times as big. But because your vision
depends upon an inverse-square law, the nearer hand
should appear twice as tall and twice as wide, and therefore occupy four times as much of your visual ?eld, as the
is so strong that you likely overrule this information. Now
if you overlap your hands slightly and view them with one
eye closed, you?ll see the nearer hand as clearly bigger.
This raises an interesting question: What other illusions do
you have that are not so easily checked?
(We all have illusions and misconceptions about many things, particularly other people and other
cultures. This idea may stimulate student discussion.)
CONCEPTUAL PHYSICS
Chapter 13 Universal Gravitation
69
Name
Class
Date
Concept-Development
Practice Page
13-2
Force and Weight
1. An apple that has a mass of 0.1 kilogram has the same mass wherever it is. The amount of matter
that makes up the apple
(depends upon) (does not depend upon)
the location of the apple. It has the same resistance to acceleration wherever
it is?its inertia everywhere is
(the same) (different).
The weight of the apple is a different story. It may weigh exactly 1 N in San Francisco and slightly
less in mile-high Denver, Colorado. On the surface of the moon the apple would weigh 1/6 N, and
far out in outer space it may have almost no weight at all. The quantity that doesn?t change with
location is
(mass) (weight),
and the quantity that may change with location is its
(mass) (weight).
That?s because
(mass) (weight)
is the force due to gravity on a body, and this force varies with distance. So weight is the force of
gravity between two bodies, usually some small object in contact with Earth. When we refer to the
(mass) (weight)
of an object we are usually speaking of the gravitational force that attracts it to Earth.
Fill in the blanks.
2. If we stand on a weighing scale and ?nd that we are pulled toward Earth with a force of 500 N, then
we weigh
500
N. Strictly speaking, we weigh
500
N relative to Earth. How much does
Earth weigh? If we tip the scale upside down and repeat the weighing process, we can say that we
and Earth are still pulled together with a force of
500
6,000,000,000,000,000,000,000,000-kg Earth weighs
500
N, and therefore, relative to us, the whole
N! Weight, unlike mass, is a relative
quantity.
CONCEPTUAL PHYSICS
Chapter 13 Universal Gravitation
71
3. The spaceship is attracted to
both the planet and the
planet?s moon. The planet
has four times the mass of its
moon. The force of attraction
of the spaceship to the planet
is shown by the vector.
a. Carefully sketch another
vector to show the
spaceship?s attraction to
the moon. Then use the
parallelogram method of
Chapter 3 and sketch the resultant force.
b. Determine the location between the planet and its moon where gravitational forces cancel.
Make a sketch of the spaceship there.
4. Consider a planet of uniform density that has a straight tunnel from the North Pole through the
center to the South Pole. At the surface of the planet, an object weighs 1 ton.
a. Fill in the gravitational force on the object when it is half way to the center, then at the center.
1/2
b. Describe the motion you would experience if you fell into the tunnel.
To and fro (in simple harmonic motion).
5. Consider an object that weighs 1 ton at the surface of a planet, just before the planet
gravitationally collapses. (The mass of the planet remains the same during collapse.)
a. Fill in the weights of the object on the planet?s shrinking surface at the radial values shown.
1
4
100
b. When the planet has collapsed to a tenth of its initial radius, a ladder is erected that puts the
object as far from its center as the object was originally. Fill in its weight at this position.
CONCEPTUAL PHYSICS
72
Chapter 13 Universal Gravitation
0
Name
Class
Date
Concept-Development
Practice Page
9-3
Momentum and Energy
0 m/s
t=0s
v=
momentum = 0 kg?m/s
t=1s
v = 10 m/s
momentum = 1000 kg?m/s
Bronco Brown wants to put Ft = ?mv to
the test and try bungee jumping. Bronco
leaps from a high cliff and experiences
free fall for 3 seconds. Then the bungee
cord begins to stretch, reducing his speed
to zero in 2 seconds. Fortunately, the cord
stretches to its maximum length just short
of the ground below.
Fill in the blanks. Bronco?s mass is 100 kg.
Acceleration of free fall is 10 m/s2.
t=2s
v = 20 m/s
momentum = 2000 kg?m/s
Express values in SI units (distance in m,
velocity in m/s, momentum in kg?m/s,
impulse in N?s, and deceleration in m/s2).
The 3-s free-fall distance of Bronco just
before the bungee cord begins to stretch
45 m
=
.
?mv during the 3-s interval of free fall
=
t=3s
v=
30 m/s
momentum = 3000 kg?m/s
3000 kg?m/s
.
?mv during the 2-s interval of slowing
down
=
3000 kg?m/s
.
Impulse during the 2-s interval of
slowing down
=
3000 N?s
.
Average force exerted by the cord during
the 2-s interval of slowing down
=
t=5s
v=
momentum =
0 m/s
0 kg?m/s
1,500 N
.
How about work and energy? How much
KE does Bronco have 3 s after his jump?
45,000 J
How much does gravitational PE
decrease during this 3 s?
45,000 J
What two kinds of PE are changing during the slowing-down interval?
Gravitational and elastic potential energies
CONCEPTUAL PHYSICS
Chapter 9
Energy
51
Energy and Momentum
A compact car and a full-size sedan are initially at rest on a horizontal parking lot at the edge of a
steep cliff. For simplicity, we assume that the sedan has twice as much mass as the compact car.
Equal constant forces are applied to each car and they accelerate across equal distances (we ignore the
effects of friction). When they reach the far end of the lot the force is suddenly removed, whereupon
they sail through the air and crash to the ground below. (The cars are beat up to begin with, and this
is a scienti?c experiment!)
1. Which car has the greater acceleration? Compact (same force but less mass)
2. Which car spends more time along the surface of the lot? Sedan (slower)
3. Which car is moving faster when it reaches the edge of the cliff?
Compact
4. Which car has the larger impulse imparted to it by the applied force? Defend your answer.
Sedan; same force applied over a longer time produces more impulse.
5. Which car has the greater momentum at the edge of the cliff? Defend your answer.
Sedan; greater impulse means greater change in momentum.
the same.
7. Which car has the greater kinetic energy at the edge of the cliff? Does
answer to 4? Why or why not?
Same KE for each; this follows from 6 where work done is same
on each. No contradiction because greater momentum of sedan
is due to its greater mass.
8. Which car spends more time in the air, from the edge of the cliff to the ground below? Both same
9. Which car lands farthest horizontally from the edge of the cliff onto the ground below? Compact
10. Challenge: Suppose the slower car crashes a horizontal distance of 10 m from the ledge. Then at
what horizontal distance does the faster car hit?
14.1 m; the compact moves ?2 faster horizontally than the sedan. [Equal KEs at top; 1/2(2m)v2 =
1/2 mV 2, where V = ?2 v, or 1.41 times faster (and farther horizontally in the same time).]
CONCEPTUAL PHYSICS
52
Chapter 9 Energy
6. Which car has the greater work done on it by the applied force? Defend
Same work on each, because the product of force and distance is
Name
Class
Date
Concept-Development
Practice Page
5-1
Projectile Motion
1. Above left: Use the scale 1 cm:5 m and draw the positions of the dropped ball at 1-second intervals.
Neglect air drag and assume g = 10 m/s2. Estimate the number of seconds the ball is in the air.
4
seconds
2. Above right: The four positions of the thrown ball with no gravity are at 1-second intervals. At
1 cm:5 m, carefully draw the positions of the ball with gravity. Neglect air drag and assume
g = 10 m/s2. Connect your positions with a smooth curve to show the path of the ball. How is
the motion in the vertical direction affected by motion in the horizontal direction?
Vertical motion is affected only by gravity; horizontal motion does not affect vertical motion.
CONCEPTUAL PHYSICS
Chapter 5
Projectile Motion
19
4. Suppose that you are an accident investigator and you are asked to ?gure whether or not the car
was speeding before it crashed through the rail of the bridge and into the mudbank as shown. The
speed limit on the bridge is 55 mph = 24 m/s. What is your conclusion?
The car was traveling at 24 m/s after it crashed through the rail. (It covered 24 m in a time of
1 s, the time to fall vertically 4.9 m.) Therefore it must have been traveling faster than 24 m/s
before hitting the rail, for some speed is lost in crashing through the rail. Therefore, the
driver was speeding.
CONCEPTUAL PHYSICS
20
Chapter 5
Projectile Motion
3. This time the ball is thrown below the horizontal. Use the same scale 1 cm:5 m and carefully draw
the positions of the ball as it falls beneath the dashed line. Connect your positions with a smooth
3.5
curve. Estimate the number of seconds the ball remains in the air.
s
Question 1 (2 points)
Listen
Two identical objects in outer space have a head-on collision and stick together. If,
before the collision, one had been moving at 5 m/s in the positive direction and the
other was moving at 2 m/s in the opposite direction, their combined speed after the
collision would be
m/s. (Answer to two decimal places.)
Question 2 (2 points)
Listen
Two canon balls are fired from ground level. One is fired at a velocity of 25 m/s at an
angle of 20 degrees. The other is fired at a velocity of 25 m/s at an angle of 70
degrees. The canon ball to hit the ground first will be the one fired at (neglecting air
resistance)
20 degrees
70 degrees
Both hit at the same time.
Question 3 (2 points)
Listen
A lunar month is about 28 days (roughly the time it takes to orbit the Earth). If the
moon were farther from the Earth than it is now, the lunar month would be
Less than 28 days.
More than 28 days.
Question 4 (2 points)
Listen
Calculate the impulse that occurs when an average force of 9 N is exerted on a cart
for 4.0 seconds. The impulse is
N*s. (Answer to two decimal places.)
Question 5 (2 points)
Listen
If an object is raised 3 times as high, its potential energy will be
much as it was at the original height. (Answer to two decimal places.)
times as
Next Page
Page 1 of 8
Question 6 (3 points)
Listen
In the Stopping Distances Lab you tested different rules given to drivers so that they
leave enough space between their car and the car in front of them. Two of the most
common driving rules are following by three seconds, and following by one car
length. Please explain which rule is better and why.
oo
Paragraph
? ? ?
?
Ea Cha
Question 9 (2 points)
Listen
A6 kg ball has a momentum of 11 kg*m/s. The ball?s speed is
to two decimal places.)
Question 10 (2 points)
Listen
A9 kg blob of putty is moving at 8 m/s and slams into a 9 kg blob of putty at rest.
Calculate the speed of the two stuck-together blobs of putty immediately after
colliding. The magnitude of the speed of the two blobs of putty stuck together is
m/s. (Answer to two decimal places.)
Question 7 (2 points)
Listen ?
A projectile is launched at ground level an angle of 15 degrees above the horizontal
and lands down range. The angle of _________ degrees at the same speed would
produce the same down-range distance, assuming no air drag. Answer to two
decimal places.
Question 8 (2 points)
Listen
A 2 kg chunk of putty moving at 3 m/s collides with and sticks to a 5 kg ball that is
initially at rest on a frictionless surface. The speed of the putty (and ball) after ward
is m/s. (Answer to two decimal places.)
Question 11 (9 points)
Listen
Below is a diagram of a 1-kg block freely sliding down a ramp. Please calculate the
potential energy (PE), kinetic energy (KE), and total energy (Total E) of the block at
each of the positions shown below. Be sure to include correct units!
units?? etc.
a) PE
b) KE =
c) Total E
d) PE =
e) KE
f) Total E=
g) PE =
h) KE
i) Total E
i) PE =
k) KE =
1) Total E-
100 m
80m
m) PE
n) KE =
o) Total E=
60m
40m
p) PE =
4) KE =
r) Total =
20 m
Question 12 (2 points)
Listen
An astronaut, floating alone in outer space, throws a baseball. If the ball floats away
at a speed of 20 meters per second, the astronaut will
Move in the opposite direction at a speed of 20 m/s.
Move in the opposite direction, but at a lower speed.
Not move as stated in any of the above choices.
Move in the opposite direction but at a higher speed.
Question 13 (2 points)
Listen
If the radius of the Earth somehow increased with no change in mass, your weight
would
Decrease.
Increase.
Not change.
Question 14 (2 points)
Listen
Calculate the power needed to lift a 490 N object 1.1 in 2.8 seconds. The power is
W. (Answer to two decimal places.)
Question 15 (2 points)
Listen
If you do work on an object in 9 times the usual time, you power output is
times the usual power output. (Answer to two decimal places.)
Question 16 (2 points)
Listen
Padded dashboards in cars are safer in an accident than non-padded ones because
an occupant hitting the dash has a lower force of impact because of the:
Increased time of impact.
Decreased time of impact.
Increased momentum.
Decreased impulse.
Question 17 (2 points)
Listen
A 2,861 N pile driver ram falls 11 m and drives a post 0.1 m into the ground. The
average impact force on the ram is N. (Answer to two decimal places.)
Question 18 (2 points)
Listen
j
A TV set is pushed a distance of 8 m with a force of 23 N. The set had
of work done on it. (Answer to two decimal places.)
Question 19 (2 points)
Listen
A stone is thrown horizontally from the top of a cliff. 2 seconds after it has left your
hand its vertical distance below the top of the cliff is ____ m. (Answer to two
decimal places.)
Question 20 (4.5 points)
Listen
VALUES OF HORIZONTAL AND VERTICAL VECTORS
A ball with a mass of 2 kg is tossed from a cliff and has initial velocity components
40 m/s vertical, and 30 m/s horizontal. The location of the ball is shown at 1-
second intervals. Air resistance is negligible, and g = 10 m/s? Give the proper
units and sign for each answer at each position.
including sign and units, ?.. etc. For all answers a tor.
g) V, ? ?
h) V-
e) V-
f) V-
i) V =
j) VX
c) V-
d) V, ?
k) V, ?
IV. =
a) V-
b) VX
m) V-
n) V-
40
W-40 m/s
Vx+30 m/s
o) V,
p) V-
30 m
q) V,
r) V-
Question 21 (2.25 points)
Listen
DISCUSSION OF VERTICAL VECTORS
Please refer to the image below with initial velocity vectors of 40 m/s vertical and 30
m/s horizontal
As the ball is thrown, if you were to draw the vertical component vectors on the
image ? please describe what they would look like throughout the path:
For example:
? please describe if the length stays the same or changes and if so how
? please describe which direction they point or if the direction changes and if so how.
40 m/s
W +40 mis
Vx+30 mis
30 m
Question 22 (3 points)
Listen
In the Projectile Motion Lab you looked at the projectile motion of objects shot at
various velocities and at various angles. If you fired two canon balls at the same
velocity and angle ? one with air resistance and one without air resistance. Are there
differences in the paths for these two canon balls? Explain your answer.
Format
? ? ?
Ea
Question 23 (2 points)
Listen
A4 kg mass has 46 J of potential energy with respect to the ground. It is
approximately ______ m above the ground. (Answer to two decimal places.)
Question 24 (4 points)
Listen
Please match the physical concept with the appropriate units.
Weight
Force
1. kg
Acceleration
2. m
Power
3. m/s
Work
4. m/s/s
DDDDDDD
Impulse
5. N
6. kg*m/s
Momentum
7. J
Energy
8. W
Mass
Velocity
Question 25 (3 points)
Listen
DISCUSSION OF NET FORCE ON PROJECTILE
Please refer to the image of projectile motion below that has initial velocity vectors of
40 m/s vertical, and 30 m/s horizontal shown at 1 second intervals.
What is the net force on the ball at its highest point? (Mention its units and direction
also.) The mass of the ball is 2 kg.
40 ms
W-40 ms
W 30 mis
30 m
Question 26 (2 points)
Listen
Calculate the kinetic energy of a 6 kg toy cart that moves at 3.1 m/s. The kinetic
energy is J. (Answer to two decimal places.)
Question 27 (2 points)
Listen
If you push and object a given distance, while applying 3 times the force, you do
times the amount of work. (Answer to two decimal places.)
Question 28 (2 points)
Listen
A projectile is fired vertically from the surface of the Earth at 5 km/s. The projectile
will
Go into an elliptical orbit about the Earth.
Go into a circular path about the Earth.
None of these
Rise and fall back to the Earth?s surface.
Question 29 (2 points)
Listen
From Earth, one satellite appears to overtake another. The slower satellite is
Higher
Can?t say.
Smaller.
Lower.
Question 30 (2 points)
Listen
A prize fighter?s gloved fist can do less damage to a jaw than an ungloved fist. The
reason for this is that the ungloved fist
Delivers an impulse to the jaw over a longer time.
Has less air resistance.
Exerts an impulse to the jaw over a shorter time.
None of these
Question 29 (2 points)
Listen
From Earth, one satellite appears to overtake another. The slower satellite is
Higher
Can?t say.
Smaller.
Lower.
Question 30 (2 points)
Listen
A prize fighter?s gloved fist can do less damage to a jaw than an ungloved fist. The
reason for this is that the ungloved fist
Delivers an impulse to the jaw over a longer time.
Has less air resistance.
Exerts an impulse to the jaw over a shorter time.
None of these
Question 31 (2 points)
Listen
Two bil?

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