Download ExamIIRevFa06

RIII-1. An elevator is going up at a constant speed. Near the top
floor, it
starts to slow to a stop. During the period that it is slowing down,
its acceleration is
A) downward.
B) upward.
C) in some other direction.
RIII-2. Consider the vectors V1 and V2 shown.
What is the direction of V = V2 – V1
V1 + V = V2
v1
direction of v?
D
v2
C
A
B

RIII-3. Consider the vector A
Which equation is correct?
A) Ax = +A cos
B) Ax = –A cos
C) Ax = +A sin
D) Ax = –A sin
y
A

x
RIII-4. A projectile is fired at an initial speed of vo at an angle of 
above the horizontal. Which of the following expressions could
possibly be the correct expression for the range of the projectile?
(Hint) check the units).
A) x  2g v0 tan 
vo2
C) x 
sin  2 
g
B) x  2g 2 vo sin(2)
D) x 
g
sin  2 
2
vo
RIII-5. A plane in horizontal flight moving at constant velocity
drops a heavy package while approaching the border of a kingdom.
Which crosses the border first? (As usual, assume that air
resistance is negligible.)
A) the plane
B) the package
C) both cross at the same instant
v = constant
border
RIII-6. A boy of mass M = 50 kg pushes on a baby carriage of
mass M/5 = 10 kg. The force on the carriage from the boy has
magnitude FonCarriage. The force on the boy from the carriage
handle has magnitude FonBoy. How do the forces compare?
A) FonCarriage = 5 FonBoy
C) FonCarriage = FonBoy
B) FonCarriage = 0.2 FonBoy
RIII-7. A heavy–duty truck pulling a light trailer is accelerating
forward. How does the force on the truck FonTruck from the trailer
compare to the force on the trailer FonTrailer from the truck?
a
A) FonTruck > FonTrailer
C) FonTrailer = FonTruck
B) FonTrailer > FonTruck
RIII-8. In the 1600's, Otto Van Güricke, a physicist in Magdeburg,
fitted two hollow bronze hemispheres together and removed the air
from the resulting sphere with a pump. Two eight-horse teams
could not pull the spheres apart, even though the hemispheres fell
apart when air was re-admitted. Suppose von Güricke had tied both
teams of horses to one side and bolted the other side to a heavy tree
trunk. In this case the tension in the rope would be...
A) twice
B) exactly the same as
C) half what it was before.
RIII-9. A box of mass m is sitting at rest on a horizontal table.
The magnitudes of the normal force N and the weight mg are
equal:
N = mg.
True(A) or false(B): The forces N and mg are a Newton's Third
Law action–reaction pair.
RIII-10. A crate of mass m rests on a rough surface with
coefficient of kinetic friction K. A horizontal force F is applied
which maintains a constant acceleration a. What is the size of that
force?
a
 
m
A) F = ma + mg
C) ma
E) None of these.
F
B) F = ma – mg
D) (ma + mg)/
RIII-11. A crate of mass m is accelerated to the left with a string at
an angle q above the horizontal. The coefficient of kinetic friction
is K. The coordinate system has been chosen as shown. What is
the correct y–equation?
y
F
x
a

K
A) F  N  mg  0
C) Fsin   N  mg  0
E) None of these
B) Fcos   K N  ma
D) Fcos   N  mg  0
RIII-12. A stationary crate is pulled to the left with a horizontal
cord. The tension in the cord is T and the crate is not moving. The
coefficient of state friction is S. Which of the following
statements must be true?
T
S
I. The magnitude of the force of friction is T.
II. The magnitude of the force of friction is SN.
III.The magnitude of the force of friction is Smg.
A) All 3 statements must be true.
B) All 3 statements are not necessarily true.
C) Only 1 of the 3 statements must be true.
D) Only 2 of the 3 statements must be true.
RIII-13. Consider the two equations in two unknowns x and y)
3x – y = 0
What is x?
A) 2
B) 3
x+y= 2
C) 1/4
D) 4
E) None of these
RIII-14. A rider in a "barrel of fun" finds herself stuck with her
back to the wall. The free-body diagram is shown.
Is the following statement definitely true for this situation?
sN=mg
A) Yes, it is certainly true. B) No, it might not be true.
RIII-15. The free-body diagram for a car rounding a banked curve
is shown. The car is going so fast that it is about to slip. The
coordinate system has been chosen.
y
a
N
x


SN mg
What is the correct y-equation?
A) N sin + sN cos – mg = 0 B) N – sN sin – mg cos = 0
C) N – mg cos = 0
E) None of these
D) N cos – sN sin – mg = 0
RIII-16. What is the magnitude of the force of gravity exerted on
the Earth by an apple that is falling from a tree to the ground?
A) mg
B) > mg
C) < mg
m
RIII-17. For a small mass m on the surface of a planet of mass M
GMm
= mg ?
and radius R, is it always true that
R2
A) Yes, this is always true regardless of whether the mass m is in
free-fall or not.
B) No, this is not always true.
RIII-18. Astronaut Dave Bowman accidentally drops his coffee
cup while eating breakfast inside the rotating centrifuge of the
spacecraft Discovery. What happens to the coffee cup?
A) the cup hangs in space before Bowman's face.
B) the cup accelerates toward the floor and smashes into little bits.
C) the cup travels in a straight line at constant speed until hitting
something and smashing into little bits.
RIII-19. Recall that Kepler's 2nd law says that planets move faster
when closer to the Sun. (KII: A line drawn from the sun to the
planet sweeps out equal areas in equal times). A small planet of
mass m is in elliptical orbit about a large star of mass M. Which of
the following statements is always true as the planet orbits the
star?
m
M
1. The direction of the acceleration of the planet is toward the star.
2. The magnitude of the acceleration of the planet is a = v2/r ,where
v is the speed of the planet and r is the distance between the planet
and the star.
3. The magnitude of the force between the planet and the star is
constant.
4. The speed of the planet is constant.
A) All are true always.
B) None are true always.
C) Only 1 and 2 are true always. D) Only 1 is true always.
E) Some other combination.