The Medical College - Page 41
What is the average total friction force that
acted
over the 8 m distance?
A.
10 N
C.
40 N
B.
20 N
D.
60 N
99.
A student stands on a rotating frictionless
stand
with two large weights in his hands. While
hold-
ing his arms in close to his sides, another
student
starts him spinning with a rotational
angular
velocity of 0.3 rev/sec. He then sticks his
arms
out straight at shoulder height and his
angular
velocity slows to 0.2 rev/sec. What is the ratio
of
his moment of inertia about his vertical spin
axis
when his arms are extended to his moment
of
inertia when his arms are at his
sides?
A.
0.6
C.
1.5
B.
0.8
D.
2.5
100.
A student-cart has a mass of 80 kg and an
initial
speed of 2 m/sec. Another student then drops
a
20 kg bag of sand onto the lap of the student
on
the cart. What is the new velocity of the
student-
cart-bag?
A.
0.9 m/sec
C.
1.2 m/sec
B.
1.0 m/sec
D.
1.6 m/sec
101.
Two students whose cart-student masses are
120
kg and 80 kg sit on the essentially
frictionless
carts. They hold the ends of a light rope and
pull
until the carts bump together. They meet at
their
common center-of-mass. If they start 2 m
apart,
how far from the starting point of the
heavier
120 kg mass is the meeting point?
A.
0.4 m
C.
1.2 m
B.
0.8 m
D.
1.4 m
102.
One student-cart of mass 80 kg has an
initial
speed of 4 m/sec and collides with another
80
kg student-cart that is at rest. The two
carts
lock together (due to a coupling
mechanism)
and move off together. What is their
common
velocity?
A.
0.5 m/sec
C.
2 m/sec
B.
1 m/sec
D.
2.5 m/sec
103.
A student-cart of mass 100 kg is accelerated
at
0.8 m/sec
2 by the falling mass
system that sup-
plies a horizontal force of 90 N to a
cord
attached to the front of the cart. What is the
fric-
tion force opposing the motion?
A.
3 N
C.
60 N
B.
10 N
D.
90 N
104.
The 90 N force that accelerates the cart at
0.8
m/sec
2 in the above problem
is supplied by the
tension in a cord passing over a frictionless
pul-
ley system to a weight that falls vertically.
What
is the mass of the falling weight?
A.
5 kg
C.
40 kg
B.
10 kg
D.
100 kg
105.
In another trial, an 80 kg student-cart is to
be
accelerated from rest over a 10 m distance.
The
students calculate that the net force
(including
the tension in the cord and the opposing
friction
force) accelerating the cart is 100 N. What is
the
speed of the 80 kg student-cart at the end of
the
10 m distance?
A.
2 m/sec
C.
5 m/sec
B.
4.5 m/sec
D.
10 m/sec
Passage VI (Questions 106–110)
Water is a weakly ionized compound having a
Ka =
1.0
10
–14. In the
absence of added H+ or OH– ions,
the [H+] = [OH
–]. (It is
recognized, of course, that H+
actually is present for the most part in
hydrated form as
H3O
+.) The K
a of benzoic acid is
6.6
10
–5.
106.
The pH of pure water is:
A.
3.0
C.
7.0
B.
5.0
D.
9.0
107.
Addition of 0.0001 moles of benzoic acid to
a
beaker containing 1 liter of water will result
in
benzoic acid solution of pH:
A.
between 3 and 4.
B.
between 4 and 5.
C.
between 5 and 6.
D.
between 6 and 7.
108.
The pOH in question 107 would be:
A.
between 4 and 5.
B.
between 5 and 6.
C.
between 6 and 7.
D.
greater than 7.
109.
If 1
10
–12 moles of
benzoic acid are dissolved
in one liter of water, the pH will be
about:
A.
6.
C.
8.
B.
7.
D.
9.
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