Physics 101.001 Test 3 - Answers April 20, 2001
Read each question and its set of answers very
carefully. There is only one best
answer for each question. Don’t be
afraid to ask questions of me during the exam.
Just raise your hand if you have one.
Ignore the questions in red. They relate to material covered later in the
course.
1. A bullet fired horizontally hits the ground
in 1 second. Neglecting air resistance,
if it had been fired with a higher speed in the same direction, it would have
hit the ground
(a) in more
than 1 second
(b) in less
than 1 second
(c) in 1
second
2. An object is thrown horizontally in the
absence of air resistance at a speed of 40 ft/s. What is its range if an identical object is
dropped from the same height and requires 2 s to hit the ground?
(a) not enough
information is given to find the range
(b) 20 ft
(c) 40 ft
(d) 80 ft
3. What is the path of an object launched from
the earth at a speed greater than the escape velocity?
(a) elliptical
(b) hyperbolic
(c) parabolic
4. A projectile is launched upward at an angle
of 750 from the horizontal and strikes the ground a certain distance
down range. What other angle of launch
at the same launch speed would produce the same distance? (Neglect air resistance.)
(a) 450
(b) 150
(c) 250
5. The escape velocity for the moon is the escape velocity for the earth.
(a) the same
as
(b) greater
than
(c) less than
6. Two bugs are riding on a spinning 331/3 rpm
record. Bug A is two inches away from
the center of the record and the Bug B is 6 inches from the center. Which bug has the greater angular velocity?
(a) A
(b) B
(c) both have the same angular velocity
7. In the absence of air resistance the
horizontal motion of a projectile at the surface of the earth is one of
constant speed.
(a) True
(b) False
8. Who classified motion into violent and
natural?
(a) Aristotle
(b) Galileo
(c)
(d) Copernicus
9. A ball rolling along a horizontal
frictionless plane would
(a) accelerate
indefinitely
(b) roll until the force
used to roll it was used up
(c) roll indefinitely at
a constant speed
10. What is the average velocity of a horse that
gallops a round‑trip distance of 15 km in a time of 30 min?
(a) 0
(b) 0.5 km/hr
(c) 30 km/hr
(d) 500 m/s
(e) None of the above
11. A young lady walks 40 m east then 30 m
north. She therefore walked a distance
of and the magnitude of her displacement was .
(a) 70 m,
50 m
(b) 70 m,
70 m
(c) 50 m,
70 m
(d) 70 m,
35 m
12. A car goes from zero to 50 m/s in
10 s. What is its average
acceleration?
(a) 9.8 m/s2
(b) 32 ft/s2
(c) 50 m/s
(d) 5 m/s2
13. A body falls from rest. If air resistance is negligible, what is the
velocity of the body after falling for 1.25 s?
(a) 2.25 ft/s
(b) 4.5 ft/s
(c) 32 ft/s
(d) 36 ft/s
(e) 40 ft/s
14. An object is in free fall. At one instant it is traveling at a speed of
50 ft/s downward. Exactly one second
later its speed is
(a) 32 ft/s
(b) 50 ft/s
(c) 82 ft/s
(d) 88 ft/s
(e) 100 ft/s
15. An object dropped from rest in free fall
will fall feet in the first second and feet in the second second.
(a) 16, 48
(b) 16, 32
(c) 32, 32
(d) 32, 64
(e) 32, 48
16. Which of the following is true about
momentum?
(a) it is a vector
(b) it is a product of
mass times velocity
(c) impulses are
required to change it
(d) all of the above
(e) none of the above
17. What is an impulse?
(a) same as momentum
(b) force times distance
(c) distance times time
(d) force times the time
which the force acts
(e) none of the above
18. If a nonzero net impulse is applied
to an object, what can one expect?
(a) while the impulse is
applied the object accelerates
(b) the impulse causes a
change in momentum of the object
(c) while the impulse is
applied the object’s velocity changes
(d) All of the above
(e) None of the above
19. Why does a person who jumps from an elevated
position bend his knees when he hits the floor?
Because
(a) he is increasing the
force acting on his body
(b) he is destroying
energy
(c) the force of impact
causes his body to bend his knees
(d) he is extending the
time during which his momentum is changing
20. A rubber ball and a lump of clay approach a
wall with the same momentum. The clay
sticks to the wall and the ball bounces off.
Which delivers the most punch (impulse) to the wall?
(a) ball
(b) clay
(c) both deliver the
same amount of punch
21. In which type of collision is energy
conserved?
(a) elastic
(b) inelastic
(c) totally inelastic
(d) All of the above
(e) None of the above
22. Two trucks of equal mass are moving toward
each other along a straight line with speeds of 50 mi/h and 60 mi/h. Assuming their collision is totally
inelastic, what is the speed of each truck after collision?
(a) each has a speed of
5 mi/h
(b) each has a speed of
10 mi/h
(c) each has a speed of
55 mi/h
(d) they just swap
original speeds
(e) each has a speed of
100 mi/h
23. Every body continues in its state of rest,
or of uniform motion in a straight line, unless it is compelled to change that
state by forces impressed upon it. This
is
(a)
(b)
(c) Galileo's "Principia" law
(d) Aristole's law of
"De Revolutionibus"
(e) Copernicus' geocentric universe
24. Suppose you have two identical sealed cans,
one filled with lead and the other empty, and you are in an orbiting space ship
where the two cans are "weightless."
How could you tell which has the greater mass?
(a) put them on a
balance
(b) throw each of them
at the guy who made up this question, if he is aboard
(c) measure their
volumes
(d) do a free-fall
experiment
(e) none of the above
25. A mass of 6 kg on the earth would have a
mass of 1 kg on the moon because the moon's gravity is 1/6 that of
earth’s.
(a) True
(b) False
26. A car moving along a straight road has a
constant acceleration of 5 mi/hr/sec. What is its change in velocity after 5
sec?
(a) 5 mi/hr
(b) 20 mi/hr
(c) 1 mi/hr
(d) 25 mi/hr
(e) you need to know the
cars initial velocity to answer this question
27. In the story of the wicked king, beautiful princess,
and handsome prince, what happened to the force on the beam when the prince
tied the rope to the hook on the side of the castle wall?
(a) the force on the beam was
cut in half
(b) the force on the
beam was doubled
(c) the force on the
beam did not change with this act
28. What is the magnitude of the acceleration of
a 2 kg object when the net force on the object is 10 N?
(a) 10 m/s2
(b) 20 m/s2
(c) 5 m/s2
29. If you stand with your weight evenly
distributed over two bathroom scales, what will be the reading on each scale
compared to your weight?
(a) each scale will
record your true weight
(b) each scale will
record one half of your true weight
30. What is implied when an object is said to be
in free fall?
(a) it has constant
velocity
(b) no forces are acting
on it
(c) only the earth
exerts a force on it
(d) air resistance is
small
31. Suppose with 200 N of force applied
horizontally to your 1500 N refrigerator that it slides across your kitchen
floor at constant velocity. The friction
forces on the floor against the refrigerator must be
(a) zero
(b) 200 N
(c) 1300 N
(d) 1500 N
(e) greater than 1500 N
32. Both a heavy man and a light man parachute
together from a high-flying plane. The first
man to attain zero acceleration will be
(a) light man
(b) heavy man
(c) both will attain
zero acceleration at the same time
33. A person is attracted toward the center of
the earth by a gravitational force of 500 N.
The force with which the earth is attracted toward the person is
(a) 500 N
(b) infinitesimally
small
(c) billions and
billions of tons