Transcript 1st SemesterExam Physics

1st Semester Exam Physics 2011-2012
1. A book is lying
at rest on a table.
The book will
remain there at
rest because:
A) there is a net force but the book has too
much inertia
B) there are no forces acting on it at all
C) it does move, but too slowly to be seen
D) there is no net force on the book
E) there is a net force, but the book is too
heavy to move
A book is lying at
rest on a table.
The book will
remain there at
rest because:
A) there is a net force but the book has too
much inertia
B) there are no forces acting on it at all
C) it does move, but too slowly to be seen
D) there is no net force on the book
E) there is a net force, but the book is too
heavy to move
There are forces acting on the book, but the only
forces acting are in the y-direction. Gravity acts
downward, but the table exerts an upward force
that is equally strong, so the two forces cancel,
leaving no net force.
2. Below you see two cases: a
physics student pulling or
pushing a sled with a force F
which is applied at an angle q.
In which case is the normal
force greater?
A) case 1
B) case 2
C) it’s the same for both
D) depends on the magnitude of
the force F
E) depends on the ice surface
Case 1
Case 2
2. Normal Force
Below you see two cases: a
physics student pulling or
pushing a sled with a force F
which is applied at an angle q.
In which case is the normal
force greater?
A) case 1
B) case 2
C) it’s the same for both
D) depends on the magnitude of
the force F
E) depends on the ice surface
Case 1
In Case 1, the force F is pushing down
(in addition to mg), so the normal force
needs to be larger. In Case 2, the force F
is pulling up, against gravity, so the
normal force is lessened.
Case 2
3. Climbing the Rope
When you climb up a rope,
A) this slows your initial velocity which
is already upward
the first thing you do is pull
B) you don’t go up, you’re too heavy
down on the rope. How do
C) you’re not really pulling down – it
just seems that way
you manage to go up the
rope by doing that??
D) the rope actually pulls you up
E) you are pulling the ceiling down
Climbing the Rope
When you climb up a rope,
A) this slows your initial velocity which
is already upward
the first thing you do is pull
B) you don’t go up, you’re too heavy
down on the rope. How do
C) you’re not really pulling down – it
just seems that way
you manage to go up the
rope by doing that??
D) the rope actually pulls you up
E) you are pulling the ceiling down
When you pull down on the rope, the rope pulls up on
you!! It is actually this upward force by the rope that
makes you move up! This is the “reaction” force (by the
rope on you) to the force that you exerted on the rope.
And voilá, this is Newton’s 3rd Law.
4. Vectors
If two vectors are given
A) same magnitude, but can be in any
direction
such that A + B = 0, what B) same magnitude, but must be in the same
direction
can you say about the
magnitude and direction
of vectors A and B?
C) different magnitudes, but must be in the
same direction
D) same magnitude, but must be in opposite
directions
E) different magnitudes, but must be in
opposite directions
Vectors I
If two vectors are given
such that A + B = 0, what
can you say about the
magnitude and direction
of vectors A and B?
A) same magnitude, but can be in any
direction
B) same magnitude, but must be in the same
direction
C) different magnitudes, but must be in the
same direction
D) same magnitude, but must be in opposite
directions
E) different magnitudes, but must be in
opposite directions
The magnitudes must be the same, but one vector must be pointing in
the opposite direction of the other, in order for the sum to come out to
zero. You can prove this with the tip-to-tail method.
5.
Vectors II
Given that A + B = C, and
that lAl 2 + lBl 2 = lCl 2,
how are vectors A and B
oriented with respect to
each other?
A) they are perpendicular to each other
B) they are parallel and in the same direction
C) they are parallel but in the opposite
direction
D) they are at 45° to each other
E) they can be at any angle to each other
Vectors II
Given that A + B = C, and
that lAl 2 + lBl 2 = lCl 2,
how are vectors A and B
oriented with respect to
each other?
A) they are perpendicular to each other
B) they are parallel and in the same direction
C) they are parallel but in the opposite
direction
D) they are at 45° to each other
E) they can be at any angle to each other
Note that the magnitudes of the vectors satisfy the Pythagorean
Theorem. This suggests that they form a right triangle, with vector C
as the hypotenuse. Thus, A and B are the legs of the right triangle and
are therefore perpendicular.
6.
Firing Balls I
A small cart is rolling at
constant velocity on a flat
track. It fires a ball straight
up into the air as it moves.
After it is fired, what happens
to the ball?
A) it depends on how fast the cart is
moving
B) it falls behind the cart
C) it falls in front of the cart
D) it falls right back into the cart
E) it remains at rest
Firing Balls I
A small cart is rolling at
constant velocity on a flat
track. It fires a ball straight
up into the air as it moves.
After it is fired, what happens
to the ball?
In the frame of reference of
the cart, the ball only has a
vertical component of
velocity. So it goes up and
comes back down. To a
ground observer, both the
cart and the ball have the
same horizontal velocity,
so the ball still returns into
the cart.
A) it depends on how fast the cart is
moving
B) it falls behind the cart
C) it falls in front of the cart
D) it falls right back into the cart
E) it remains at rest
when
viewed from
train
when
viewed from
ground
7.
Firing Balls II
Now the cart is being pulled
along a horizontal track by an
external force (a weight
hanging over the table edge)
and accelerating. It fires a ball
straight out of the cannon as it
moves. After it is fired, what
happens to the ball?
A) it depends upon how much the
track is tilted
B) it falls behind the cart
C) it falls in front of the cart
D) it falls right back into the cart
E) it remains at rest
Firing Balls II
Now the cart is being pulled
along a horizontal track by an
external force (a weight
hanging over the table edge)
and accelerating. It fires a ball
straight out of the cannon as it
moves. After it is fired, what
happens to the ball?
A) it depends upon how much the
track is tilted
B) it falls behind the cart
C) it falls in front of the cart
D) it falls right back into the cart
E) it remains at rest
Now the acceleration of the cart is completely unrelated to the ball. In
fact, the ball does not have any horizontal acceleration at all (just like
the first question), so it will lag behind the accelerating cart once it is
shot out of the cannon.
8.
Firing Balls III
The same small cart is
now rolling down an
inclined track and
accelerating. It fires a
ball straight out of the
cannon as it moves.
After it is fired, what
happens to the ball?
A) it depends upon how much the track is tilted
B) it falls behind the cart
C) it falls in front of the cart
D) it falls right back into the cart
E) it remains at rest
Firing Balls III
The same small cart is
now rolling down an
inclined track and
accelerating. It fires a
ball straight out of the
cannon as it moves.
After it is fired, what
happens to the ball?
A) it depends upon how much the track is tilted
B) it falls behind the cart
C) it falls in front of the cart
D) it falls right back into the cart
E) it remains at rest
Because the track is inclined, the cart accelerates. However, the ball
has the same component of acceleration along the track as the cart
does! This is essentially the component of g acting parallel to the
inclined track. So the ball is effectively accelerating down the incline,
just as the cart is, and it falls back into the cart.
9.
Dropping a Package
You drop a package from
a plane flying at constant
speed in a straight line.
A) quickly lag behind the plane
while falling
B) remain vertically under the
plane while falling
Without air resistance, the
C) move ahead of the plane while
falling
package will:
D) not fall at all
Dropping a Package
You drop a package from
a plane flying at constant
speed in a straight line.
A) quickly lag behind the plane
while falling
B) remain vertically under the
plane while falling
Without air resistance, the
C) move ahead of the plane while
falling
package will:
D) not fall at all
Both the plane and the package have
the same horizontal velocity at the
moment of release. They will maintain
this velocity in the x-direction, so they
stay aligned.
10
Dropping the Ball I
From the same height (and
at the same time), one ball
is dropped and another ball
is fired horizontally. Which
one will hit the ground
first?
(A) the “dropped” ball
(B) the “fired” ball
(C) they both hit at the same time
(D) it depends on how hard the ball
was fired
(E) it depends on the initial height
Dropping the Ball I
From the same height (and
at the same time), one ball
is dropped and another ball
is fired horizontally. Which
one will hit the ground
first?
(A) the “dropped” ball
(B) the “fired” ball
(C) they both hit at the same time
(D) it depends on how hard the ball
was fired
(E) it depends on the initial height
Both of the balls are falling vertically under the influence of
gravity. They both fall from the same height. Therefore, they will
hit the ground at the same time.
The fact that one is moving
horizontally is irrelevant – remember that the x and y motions are
completely independent !!
11.
A) the “dropped” ball
In the previous problem,
B) the “fired” ball
which ball has the greater
C) neither – they both have the
same velocity on impact
velocity at ground level?
D) it depends on how hard the
ball was thrown
Dropping the Ball II
A) the “dropped” ball
In the previous problem,
B) the “fired” ball
which ball has the greater
C) neither – they both have the
same velocity on impact
velocity at ground level?
D) it depends on how hard the
ball was thrown
Both balls have the same vertical velocity
when they hit the ground (since they are
both acted on by gravity for the same
time). However, the “fired” ball also has a
horizontal velocity. When you add the two
components vectorially, the “fired” ball
has a larger net velocity when it hits the
ground.
12
A projectile is launched
from the ground at an
angle of 30o. At what
point in its trajectory does
this projectile have the
least speed?
A) just after it is launched
B) at the highest point in its flight
C) just before it hits the ground
D) halfway between the ground and
the highest point
E) speed is always constant
12
A projectile is launched from
the ground at an angle of
30o. At what point in its
trajectory does this projectile
have the least speed?
A) just after it is launched
B) at the highest point in its flight
C) just before it hits the ground
D) halfway between the ground and
the highest point
E) speed is always constant
The speed is smallest at
the highest point of its
flight path because the ycomponent of the velocity
is zero.
13. Suppose a projectile is launched straight
up. Make a statement about the velocity and
the acceleration when the projectile reaches the
highest point.
A) Both its velocity and its acceleration are zero.
B) Its velocity is zero and its acceleration is not zero.
C) Its velocity is not zero and its acceleration is zero.
D) Neither its velocity nor its acceleration is zero.
14
Up in the Air I
You throw a ball upward with
A) more than 10 m/s
an initial speed of 10 m/s.
B) 10 m/s
Assuming that there is no air
resistance, what is its speed
when it returns to you?
C) less than 10 m/s
D) zero
E) need more information
14
You throw a ball upward with
A) more than 10 m/s
an initial speed of 10 m/s.
B) 10 m/s
Assuming that there is no air
resistance, what is its speed
when it returns to you?
C) less than 10 m/s
D) zero
E) need more information
The ball is slowing down on the way up due to
gravity. Eventually it stops. Then it accelerates
downward due to gravity (again). Since a = g on
the way up and on the way down, the ball reaches
the same speed when it gets back to you as it had
when it left.
15) Four students measure the mass
of an object, each using a different
scale. They record their results as
follows:
Which student used the least
precise scale?
A) A Student A B
C
D
Mass (g ) 49.06 49
50
49.2
B) B
C) C
D) D
16. All of the following are base units of the SI
system except:
A) kilogram.
B) kelvin.
C) meter.
D) volt.
17. Select the list which
contains only SI basic units.
A) liter, meter, second, watt
B) joule, kelvin, kilogram, watt
C) candela, kelvin, meter, second
D) joule, newton, second, watt
18. The number of significant
figures in 10001 is
A) two.
B) three.
C) five.
D) six.
19. Suppose that an object travels from one
point in space to another. Make a comparison
between the displacement and the distance
traveled.
A) The displacement is either greater than
or equal to the distance traveled.
B) The displacement is always equal to the
distance traveled.
C) The displacement is either less than or
equal to the distance traveled.
D) The displacement can be either greater
than, smaller than, or equal to the
distance traveled.
20. When is the average velocity of an
object equal to the instantaneous
velocity?
A) always
B) never
C) only when the velocity is
constant
D) only when the velocity is
increasing at a constant rate
21
You drive for 30 minutes at 30
A) more than 40 mi/hr
mi/hr and then for another 30
B) equal to 40 mi/hr
minutes at 50 mi/hr. What is your
average speed for the whole trip?
C) less than 40 mi/hr
21
You drive for 30 minutes at 30
A) more than 40 mi/hr
mi/hr and then for another 30
B) equal to 40 mi/hr
minutes at 50 mi/hr. What is your
C) less than 40 mi/hr
average speed for the whole trip?
It is 40 mi/hr in this case. Since the average speed is distance/time and
you spend the same amount of time at each speed, then your average
speed would indeed be 40 mi/hr.
22. A polar bear starts at the North Pole. It travels 1.0
km south, then 1.0 km east, then 1.0 km north, then 1.0
km west to return to its starting point. This trip takes 45
min. What was the bear's average speed?
A) 0 km/h
B) 0.09 km/h
C) 4.5 km/h
D) 5.3 km/h
23. The number of significant
figures in 0.01500 is
A) two.
B) three.
C) four.
D) five.
24. A cart starts from rest and accelerates at 4.0
m/s2 for 5.0 s, then maintain that velocity for 10
s, and then decelerates at the rate of 2.0 m/s2 for
4.0 s. What is the final speed of the car?
A) 20 m/s
B) 16 m/s
C) 12 m/s
D) 10 m/s
25. An object is thrown upward with a speed of
14 m/s on the surface of planet X where the
acceleration due to gravity is 3.5 m/s2. What is
the speed of the object after 8.0 s?
A) 7.0 m/s
B) 14 m/s
C) 21 m/s
D) 64 m/s
26. In the figure, what is the
velocity at t = 1.0 s?
A) 0
B) 10 m/s
C) 20 m/s
D) -40 m/
27. In Fig. 2-1, what is the velocity at t = 2.5
s?
A) 0
B) 10 m/s
C) 20 m/s
D) -40 m/s
28. InInFig.
Fig.2-1,
2-1,what
what
velocity
= 4.0
28.
is is
thethe
velocity
at tat= t4.0
s? s?
A) 0
B) 10 m/s
C) 20 m/s
D) -40 m/s
29. What is the product of 12.56 and 2.12?
A) 27
B) 26.6
C) 26.23
D) 26.627
30. Which of the following is an accurate
statement?
A vector
cannot
have
magnitude
if one
A) A)
A vector
cannot
have
zerozero
magnitude
if one
of its
of its components
components
is not zero. is not zero.
The
magnitude
vectorcan
canbe
beless
lessthan
thanthe
the
B) B)
The
magnitude
ofofa avector
magnitude of one of its components.
magnitude of one of its components.
C) If the magnitude of vector A is less than the
C) Ifmagnitude
the magnitude
of vector
A the
is less
than the of
of vector
B, then
x-component
magnitude
of than
vector
then the x-component
of A is
A is less
theB,
x-component
of B.
lessD)than
x-component
of B.can be positive or
Thethe
magnitude
of a vector
negative.
D) The
magnitude of a vector can be positive or
negative.
31. What is the result of 2.43 ÷ 4.561?
A) 5.3278 × 10-1
B) 5.328 × 10-1
C) 5.33 × 10-1
D) 5.3 × 10-1
32. When you sit on a chair, the resultant force
on you is
A) zero.
B) up.
C) down.
D) depending on your
weight.
33. The radius of the Earth is 3963 mi. What is
the surface area of the Earth in square meters?
(1 mi = 1609 m.)
A) 4.9 × 107 m2
B) 1.3 × 1014 m2
C) 2.6 × 1014 m2
D) 5.1 × 1014 m2
34. A 400-m tall tower casts a 600-m long
shadow over a level ground. At what angle is
the Sun elevated above the horizon?
A) 34°
B) 42°
C) 48°
D) can't be found; not enough information
35. If you blow up a balloon, and then release it,
the balloon will fly away. This is an illustration of
A) Newton's 1st law.
B) Newton's 2nd law.
C) Newton's 3rd law.
D) Galileo's law of inertia.
36. Two displacement vectors have
magnitudes of 5.0 m and 7.0 m,
respectively.
When these two vectors are added,
the magnitude of the sum
A) is 2.0 m.
B) could be as small as 2.0 m, or as large as
12 m.
C) is 12 m.
D) is larger than 12 m.
37. A ball is thrown upward at a velocity
37. of
A 19.6
ball is
thrown
at a velocity
m/s.
Whatupward
is its velocity
after of
19.6 m/s. What is3.00
its velocity
after 3.00 s?
s?
A) 9.8 m/s upward
B) 9.8 m/s downward
C) zero
D) 19.6 downward
38. The acceleration of gravity on the Moon is
only one-sixth of that on Earth. If you hit a
baseball on the Moon with the same effort (and at
the speed and angle) that you would on Earth, the
ball would land
A) the same distance away.
B) one-sixth as far.
C) 6 times as far.
D) 36 times as far.
39. A runner runs halfway around a circular
path of radius 10 m. What is the displacement
of the jogger?
A) 0
B) 5 m
C) 10 m
D) 20 m
40. In the Figure on the right, what is the
average velocity from 0 to 6.0 s?
A) 0
B) 10 m/s
C) 20 m/s
D) -40 m/s
41. In Fig. 2-2, what is the acceleration at 3.0 s?
A) 0
B) 2.0 m/s2
C) -2.5 m/s2
D) 10 m/s2
42. In Fig. 2-2, what is the average acceleration
from 0 to 8.0 s?
A) 0
B) 2.0 m/s2
C) -2.5 m/s2
D) 10 m/s2
43. In Fig. 2-2, what is the displacement
from 0 to 8.0 s?
A) 20 m
B) 40 m
C) 60 m
D) 80 m
44. In the diagram shown below, the unknown vector is
A)
B)
C)
D)
45. Ignoring air resistance, the horizontal
component of a projectile's velocity
A) is zero.
B) remains constant.
C) continuously increases.
D) continuously decreases.
46. A pilot drops a bomb from a plane
flying horizontally at a constant speed.
Neglecting air resistance, when the
bomb hits the ground the horizontal
location of the plane will
A) be behind the bomb.
B) be over the bomb.
C) be in front of the bomb.
D) depend on the speed of the plane when
the bomb was released.
47. What is the mass of an object that weighs 250
N on the surface of the Earth where the
acceleration due to gravity is 9.80 m/s2?
A) 250 kg
B) 24.5 kg
C) 25.5 kg
D) 2,450 kg
48. Can work be done on a system
if there is no motion?
A) Yes, if an outside force is provided.
B) Yes, since motion is only relative.
C) No, since a system which is not moving has no
energy.
D) No, because of the way work is defined.
49. A container of water is lifted vertically 3.0 m
then returned to its original position. If the total
weight is 30 N, how much work was done?
A) 45 J
B) 90 J
C) 180 J
D) No work was done.
50. Does the centripetal force acting on
an object do work on the object?
A) Yes, since a force acts and the object moves, and
work is force times distance.
B) Yes, since it takes energy to turn an object.
C) No, because the object has constant speed.
D) No, because the force and the displacement of the
object are perpendicular.
51. A person is standing on a scale in an
elevator accelerating downward. Compare the
reading on the scale to the person's true weight.
A) greater than their true weight
B) B) equal to their true weight
C) less than their true weight
D) zero
52. Is it possible for an object moving with a
constant speed to accelerate? Explain.
A) No, if the speed is constant then the acceleration
is equal to zero.
B) No, an object can accelerate only if there is a net
force acting on it.
C) Yes, although the speed is constant, the direction
of the velocity can be changing.
D) Yes, if an object is moving it can experience
acceleration
53. A force moves an object in the direction of the
force. The graph to the right, shows the force versus
the object's position. Find the work done when the
object moves from 0 to 2.0 m.
A) 20 J
B) 40 J
C) 60 J
D) 80 J
54. A force moves an object in the direction of the
force. The graph shows the force versus the object's
position. Find the work done when the object moves
from 2.0 to 4.0 m.
A) 20 J
B) 40 J
C) 60 J
D) 80 J
55. A force moves an object in the direction of the
force. The graph in Fig. 6-1 shows the force versus
the object's position. Find the work done when the
object moves from 4.0 to 6.0 m.
A) 20 J
B) 40 J
C) 60 J
D) 80 J
56. List the four fundamental forces in nature.
A) gravitational, normal, tension, friction
B) gravitational, normal, kinetic friction, static
friction
C) gravitational, electromagnetic, strong nuclear,
weak nuclear
D) gravitational, electromagnetic, contact, nuclear
57. A spherically symmetric planet has four times
the Earth's mass and twice its radius. If a jar of
peanut butter weighs 12 N on the surface of the
Earth, how much would it weigh on the surface of
this planet?
A) 6.0 N
B) 12 N
C) 24 N
D) 36 N
58. Which of Newton's laws best explains
why motorists should buckle-up?
A) the first law
B) the second law
C) the third law
D) the law of gravitation
59. Two forces are acting on an object as shown in the
figure. What is the magnitude of the resultant force?
A) 47.5 N
B) 185 N
C) 198 N
D) 200 N
60. Two forces are acting on an object as
shown the figure.. What is the direction of the
resultant force?
A) 12° above -x
B) 78° above -x
C) 12° above +x
D) 78° above +x
61. The speed of Halley's Comet, while
traveling in its elliptical orbit around the Sun,
A) is constant.
B) increases as it nears the Sun.
C) decreases as it nears the Sun.
D) is zero at two points in the orbit.
62.
63. Calculate the average velocity
64. Calculate the average acceleration