Physics 125
* Answer key is on the last page (no peeking until you really try it!)
Previous Exam #1
Mesa
Name: ______________________
This quiz will be closed book. You may only use a calculator. Please do not make any phone calls during this quiz.
Please have your phone turned off and put away. If your phone rings or buzzes during the quiz, you may be asked to
leave early. There are 25 multiple choice questions, 2 problems, and one bonus question. Although partial credit will
not be given for the multiple choice questions, you must show your work and calculations for those that require
numerical calculation. You must use the conventional notation that was used in class. If your work is not neat and
organized, and I cannot follow your logic, then you will not receive full credit. Use mks units unless otherwise asked.
If you have time in the end, you should go back and recheck your answers.
Remember, no work or bad physics = no credit. Take your time and relax! If there is something that is not clear,
please ask. For best results, do not round off numbers in intermediate calculations.
Complete solutions must include:
1) Diagram with the given information shown on it. All diagrams must be fully labeled.
2) Physics equations being used.
3) Substitution showing given values and units.
4) Answer or result in the box!
** use g = 9.8 m/s2 unless instructed otherwise **
*** Please mark your answers on the provided scantron and this quiz paper.
You are responsible for your final answers.
sin θ =
opposite
hypotenuse
cos θ =
adjacent
hypotenuse
tan θ =
opposite
adjacent
hypotenuse
op
θ
adj
vf = vo + at
s=
d
∆t
2
xf = xo + vo t + ½ at
constant acceleration)
v=
∆x
∆t
a=
vf2
=
vo2
+ 2a ∆x (for motion in one-dimension with
∆v
∆t
(3 Points Each)
1. Cody is driving his new turbo-car East to West along the highway when he applies the brakes.
His
a. velocity and acceleration are both East.
b. velocity and acceleration are both West.
c. velocity is West and its acceleration is East.
d. velocity is East and its acceleration is West.
2. If you drop an object in the absence of air resistance, it accelerates downward at 9.81 m/s2 in
magnitude. If instead you throw it downward, the magnitude of its downward acceleration after
release is (again, ignore air resistance)
a. less than 9.81 m/s2.
b. 9.81 m/s2.
c. more than 9.81 m/s2.
d. none of the above
1
3. A person standing at the edge of a cliff throws one ball straight up and another ball
straight down at the same initial speed. Neglecting air resistance, the ball to hit the
ground below the cliff having the greater impact speed is the one initially thrown
a. upward.
b. downward.
c. neither—they both hit at the same speed.
4. An object falling near the surface of Earth has a constant acceleration of 9.8 m/s2 . This means
that the
A) object falls 9.8 m during the first second of its motion.
B) object falls 9.8 m during each second of its motion.
C) speed of the object increases by 9.8 m/s during each second of its motion.
D) acceleration of the object increases by 9.8 m/s2 during each second of its motion.
5. You are throwing a ball straight up in the air. At the highest point, the ball’s
a. velocity and acceleration are zero.
b. velocity is nonzero but its acceleration is zero.
c. acceleration is nonzero, but its velocity is zero.
d. velocity and acceleration are both nonzero.
6. Angela throws a ball straight upward from an 80-ft tower with an initial vertical speed of
40 ft/s. If air resistance is ignored, the ball’s speed when it reaches the ground will be about
(use g = 32.2 ft/s2 )
A) 67 ft/s B) 102 ft/s C) 102 ft/s D) 49 ft/s E) 82 ft/s
2
*** Please mark your answers on the provided scantron and this quiz paper.
7. What is the meaning of a horizontal line (not on the axis) on a plot of velocity vs. time?
a. The object is at rest.
b. The object is moving at constant speed.
c. The object is speeding up at a constant rate.
d. The object is accelerating at a constant non-zero rate.
e. The object is moving with increasing instantaneous speed.
For problems # 8- 10:
Consider a projectile that is launched upward at some angle between 0º and 90º with initial
horizontal (x) and vertical (y) components of velocity that are both positive. Air friction can be
neglected. The three questions that follow all refer to this projectile.
8. When the projectile reaches its maximum vertical displacement, the vertical component of its
velocity is:
A. positive
B. negative
C. zero
D. equal to the horizontal component of velocity at the same time
E. equal to the vertical component of velocity when it was launched
9. When the projectile reaches its maximum vertical displacement, the horizontal component of
its velocity is:
A. increasing
B. decreasing
C. zero
D. equal to the vertical component of velocity at the same time
E. equal to the horizontal component of velocity when it was launched
10. When the projectile reaches its maximum vertical displacement, the direction of the
projectile’s acceleration is:
A. positive x direction
B. negative x direction
C. positive y direction
D. negative y direction
E. it has no direction, the acceleration is zero
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11. The figure below represents the parabolic trajectory of a ball going from A to E in earth
gravity but without air resistance. What is the direction of the acceleration at point B?
A) It is up and to the right.
D) It is straight down.
B) It is down and to the left.
E) The acceleration of the ball is zero.
C) It is straight up.
12.
An airplane in horizontal flight releases a relief package as shown in the diagram. The
trajectory of the package is best represented by
A) 1
B) 2
C) 3
D) 4
E) None of these is correct.
13.
A projectile is fired with an initial speed of 1000 m/s at an angle of 37º above the
horizontal. If air resistance is neglected, the horizontal component of the projectile's velocity
after 20 seconds is approximately
A) 800 m/s B) 600 m/s C) 640 m/s D) 40 m/s E) 16,000 m/s
4
14. A common statistic in car tests is the standing (starting from rest) quarter-mile performance.
A modern sports car can achieve a terminal speed (speed at the end of the quarter-mile) of
120 mph (53.64 m/s). How does the average acceleration compare to g? (0.25 mile = 402 m)
A) 0.36 g
B) 2.8 g
C) 0.067 g
D) 15.0 g
E) 0.73 g
*** Please mark your answers on the provided scantron and this quiz paper. Reminder: you are responsible for
correctly filling in your Scantron form.
15. Marian drops her physics book from the top of a building. In the absence of air resistance,
the book hits the ground with a speed of 48.5 m/s. The height of the building is about
A) 25 m
B) 5 m
C) 240 m
D) 120 m
E) 10 m
16. Kristina releases a sandbag from a rising air hot-air balloon and it hits the ground
7 seconds later. From what height was the sandbag dropped from if at the moment of
release the balloon (and sandbag!) was traveling upward at 3 m/s.
A) 261 m
B) 240 m
C) 459 m
D) 219 m
E) 55 m
5
17. Sarah throws a baseball horizontally at 25 meters per second from a cliff 45 meters above the
level ground. Approximately how far from the base of the cliff does the ball hit the ground? [Neglect
the height of her hand above the cliff.]
A) 45 m
B) 76 m
C) 140 m
D) 230 m
E) 1125 m
18. Approximately what speed does the ball in problem 17 have when it hits the ground?
a) 30 m/s
b) 25 m/s
c) 0 m/s
d) 9.8 m/s
e) 39 m/s
19. If the position of an object is plotted vertically on a graph and the time is plotted horizontally,
the instantaneous velocity at a particular time is
A) the height of the curve at that time.
B) the total length of the curve.
C) the area under the curve from zero to that time.
D) the slope of the tangent line to the curve at that time.
E) impossible to determine from this type of plot.
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20. A train starts from rest and accelerates uniformly at 0.096 m/s2, until it has traveled 3.0 km
and acquired a velocity of 24 m/s. The train then moves at a constant velocity of 24 m/s for
430 s. The average speed of the train over the entire trip is about:
a) 17 m/s
b) 12 m/s
c) 24 m/s d) 20 m/s e) 16 m/s
21. Suppose the vectors A and B in the drawing have magnitudes of 6.0 m and are directed as
shown. What are Ax and Bx, the scalar components of A and B along the x axis?
a) Ax = +(6.0 m)cos35° = +4.9 m
Bx = -(6.0 m)cos35° = -4.9 m
b) Ax = +(6.0 m)sin35° = +3.4 m
Bx = -(6.0 m)cos35° = -4.9 m
c) Ax = -(6.0 m)cos35° = -4.9 m
Bx = +(6.0 m)sin35° = +3.4 m
d) Ax = -(6.0 m)cos35° = -4.9 m
Bx = +(6.0 m)cos35° = +4.9 m
e) Ax = -(6.0 m)sin35° = -3.4 m
Bx = +(6.0 m)sin35° = +3.4 m
22. Of the following situations, which one is impossible?
a) a body having velocity east and acceleration east
b) a body having velocity east and acceleration west
c) a body having zero velocity and non-zero acceleration
d) a body having constant acceleration and variable velocity
e) a body having constant velocity and variable acceleration
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For questions 23-25: Emily throws her calculator straight up from the surface of the earth with
an initial speed of 19.6 m/s. Neglect any effects due to air resistance.
23. What is the magnitude of the calculator's displacement from the starting point after
1.00 second has elapsed?
A) 9.80 m
B) 24.5 m
C) 19.6 m
D) 14.7 m
E) 58.8 m
24.
A)
B)
C)
D)
E)
8
What maximum height (above her hand) will the calculator reach?
19.6 m
14.7 m
9.80 m
24.5 m
58.8 m
25. How much time elapses between the throwing of the calculator and its return to the
original launch point?
A) 2.00 s
B) 4.00 s
C) 12.0 s
D) 8.00 s
E) 16.0 s
Reminder:
* please do not leave any questions BLANK.
* put your name on this exam paper.
* go back and erase any extraneous marks on your scantron.
* hand in both this exam paper and your scantron.
* re-check your answers. They cannot be changed after you hand in this exam.
* By signing your name on the front of this quiz, you agree to not ask for your answers to be changed after you turn
in this quiz paper. This means that if the answer to #1 is E, and you circled A, but meant to put E, your final answer
is the answer you submitted on your scantron.
*** Please mark your answers on the provided scantron and this quiz paper.
9
Problem #1 (10 points). Please read the instructions on the first page of this exam.
Accuracy counts! Please read each question very carefully.
Julie throws a stone from a cliff that is 15.0 m high. The stone follows the path shown in the
diagram. The magnitude of the initial velocity of the stone is v0 = 25.0 m/s. The horizontal
component of the initial velocity is v0x = 11.3 m/s. Assume there is no air resistance in this
problem.
a) (2pts) Draw an arrow at point P (the maximum height) that points in the direction of the
stone’s velocity at that point. Label the arrow v . If the velocity is zero, write v = 0 at
point P.
b) (2pts) What is the magnitude of the stone’s velocity at point P?
vP = _________
c) (2pts) Draw an arrow at point P that points in the direction of the stone’s acceleration at
that point. Label the arrow a . If the acceleration is zero, write a = 0 at point P.
d) (2pts) What is the magnitude of the stone’s acceleration at point P?
aP = _________
e) (2pts) Draw an arrow at point Q that points in the direction of the stone’s velocity at that
point. Label the arrow v . If the velocity is zero, write v = 0 at point Q.
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Problem #2 (15 points). You must draw and label a complete diagram. Please read the
directions on page one of this quiz.
Sang kicks a football at an angle of 58.0° above the horizontal ground. The initial speed of the
ball is 22.7 m/s. Find the maximum height that the ball attains. Ignore any effects due to air
resistance. You must show proper substitution of numerical values along with proper units and
their cancellation.
Ans:
11
(10 points!!) All or Nothing Bonus Question. No partial credit. You must show your
reasoning & work to receive full credit. Please read the question very carefully.
Mandie hits a home run for her team, and the ball lands in the left-field seats, 7.5 meters above
the point at which it was hit. It lands with a velocity of 36 m/s at an angle of 28° below the
horizontal as shown. Find the magnitude and direction of the initial velocity with which the ball
leaves the bat. (Ignore any effects due to air resistance.) Assume all data is known to 3
significant figures. You must show proper substitution of numerical values along with proper
units and their cancellation.
* Answer key is on the next page
Ans:
12
Answer Key
#1 a) b) 11.3m/s
c) down d) 9.8m/ss
e) tangent to the curve at Q.
#2: 18.9m
Bonus: vo = 37.99 m/s @ 33.2°
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