### Quiz 2014.09.12

```Suppose that a person is standing on a scale in an elevator when
the elevator begins to accelerate upward. According to Newton's
Third Law, one of the following forces will be equal and opposite
to the force the person exerts on the scale (which is what the
scale will read). Choose that force.
th
e
te
d
on
si
ex
er
ce
ef
or
0%
...
h.
..
0%
st
ei
w
No
ne
of
th
e
ch
oi
ce
er
ep
Th
0%
gh
t.
...
as
st
m
so
n'
s
er
ep
Th
so
n'
s
im
xe
ee
fo
rc
al
or
m
en
Th
0%
es
rte
.. .
0%
Th
A. The normal force exerted
on the person.
B. The person's mass times
their acceleration.
C. The person's weight.
D. None of the choices is the
appropriate third law pair.
E. The force exerted on the
scale by the elevator.
In the diagram to the right, a
ball is flying through the air
after being thrown. One of the
forces drawn on it is
inappropriate, inaccurate, or
not a real force. Which one is it?
ok
.
.
e
ar
ce
s
th
e
ll
of
he
,t
Fg
0%
ity
ra
v
fo
rc
e
fo
r
he
of
t
fo
rc
e
he
,t
Ft
0%
of
g
th
ro
w
re
ir
of
a
fo
rc
e
th
e
r,
Fa
i
0%
.
s.
..
0%
A
A. Fair , the force of air
resistance.
B. Ft , the force of the
throw.
C. Fg , the force of gravity.
D. All of the forces are ok.
Four blocks are placed on a frictionless table. A single horizontal force is
applied to each of them. The masses of the blocks and the magnitudes of the
applied forces are shown. Which of the blocks has the greatest rate of change
in velocity?
0%
Th
ey
ar
e
Bl
eq
oc
k
ua
l
4
0%
3
oc
k
oc
k
Bl
oc
k
0%
2
0%
1
0%
Bl
Block 1
Block 2
Block 3
Block 4
They are equal
Bl
A.
B.
C.
D.
E.
A person pushes two boxes with a horizontal force of
100 N on a frictionless floor. Here, m1 > m2. Which of
the following is correct?
pu
ox
es
w
n.
..
ill
th
e
of
Th
eb
ce
s
ef
or
0%
no
tb
eg
i
sh
e
ll.
.
on
us
he
s
Th
bo
xp
ue
0%
s.
.
0%
ye
ll.
.
ye
on
us
he
s
Bl
D.
bo
xp
C.
0%
ue
B.
Blue box pushes on yellow box
with 100 N force, and yellow box
pushes on blue box with 100 N
force.
Blue box pushes on yellow box
harder than yellow box pushing
on blue box.
The forces of the pushes on each
other are equal but less than 100
N.
The boxes will not begin to move
unless the total weight of the two
boxes is less than 100 N.
Bl
A.
A block sits at rest on a frictionless surface. Which of the following
sketches most closely resembles the correct freebody diagram for all
forces acting on the block? Each red arrow represents a force.
Observe their number and direction, but ignore their lengths.
A
B
C
D
0%
D
0%
C
0%
B
0%
A
A.
B.
C.
D.
Now, the same block moves with a constant velocity to the right on the
frictionless surface. Which of the following most closely resembles the
correct freebody diagram for all forces acting on the block?
0%
0%
E
0%
D
0%
C
0%
B
A
B
C
D
E
A
A.
B.
C.
D.
E.
Now, the block moves with a constant velocity to the right on a surface
that has friction. Which of the following most closely resembles the
correct freebody diagram for all forces acting on the block?
0%
0%
E
0%
D
0%
C
0%
B
A
B
C
D
E
A
A.
B.
C.
D.
E.
Given the forces acting on the object and the magnitude of its
acceleration, find the object's mass (in "kg"). No forces, other
than the ones shown, are present.
Rank
1
Responses
2
3
4
5
6
0%
1
0%
2
0%
3
0%
4
0%
5
0%
6
```