Transcript Lecture22_TwentyMoreQuestions

PHYS 115 EXAM
Wednesay, October 24
10:30-11:20pm
Brace 211
Brace 113
Brace 201
Brace 305
You draw back a rubber band 20 cm (8 inches)
and feel the 10 N force it pulls back with.
A. 0 Newtons.
B. 10 Newtons.
C. 20 Newtons.
D. 30 Newtons.
E. 40 Newtons.
Force
Hoping to shoot it all the way across the room
you pull it back a full 60 cm (24 in).
How great is the force needed to hold it there
(steady at rest)?
Distance
Hoping to shoot it all the way across the room
you pull it back a full 60 cm.
It takes 30 N of force to hold it there.
How much work did you do in stretching it?
A. 0 Joules
B. (15 N)(0.60 m) = 9 Joules.
C. (30 N)(0.60 m) = 18 Joules.
D. (45 N)(0.60 m) = 27 Joules.
E. (60 N)(0.60 m) = 36 Joules.
Hoping to shoot it all the way across the room
you pull it back a full 60 cm.
It takes 30 N of force to hold it there.
What average force did you exert in
pulling it back this far?
30 N
Force
A. 30 Newtons.
B. 20 Newtons.
C. 15 Newtons.
D. 10 Newtons.
E. 5 Newtons.
Distance
Hoping to shoot it all the way across the room
you pull it back a full 60 cm.
It takes 30 N of force to hold it there.
How much work did you do in stretching it?
A. 0 Joules
B. (15 N)(0.60 m) = 9 Joules.
C. (30 N)(0.60 m) = 18 Joules.
D. (45 N)(0.60 m) = 27 Joules.
E. (60 N)(0.60 m) = 36 Joules.
Hoping to shoot it all the way across the room
you pull it back a full 60 cm.
It takes 30 N of force to hold it there.
You performed 9 Joules of work in stretching it.
When released, the rubber band flies off
with what kinetic energy?
A. 0 Joules
B. 3 Joules.
C. 4.5 Joules.
D. 9 Joules.
E. You need to know the band’s mass.
A rider in the “barrel of fun” at the
State Fair midway has her back “pinned”
to the wall. Which diagram correctly
shows the forces acting in her?
A.
D.
B.
E.
C.
F.
In the game of tetherball,
the struck ball whirls
around a pole. In what
direction does the net
force on the ball point?
E
A
C
A. Towards the top
of the pole
B. Down, towards the
ground
C. Horizontal, in toward the pole.
D. Horizontal, out from the pole.
E. Up along the vertical component
of the tension force
E. Tangential to the circle
D
F
B
You do NOT slow down to take the
left curve in the road ahead,
or speed up at any point in it,
but instead enter and leave the turn
at exactly the same speed.
During this left turn your car is
A. moving with constant velocity.
B. accelerating backward.
C. accelerating left.
D. accelerating right.
A fighter pilot making a sharp turn will pass
out if the acceleration he experiences is more
than 9g’s (9 the acceleration of gravity).
If his F18 is moving with a speed of 300 m/s,
what is the approximate radius of the
tightest turn this pilot can survive ?
A) 500 m
B) 1000 m
C) 2000 m
The angular momentum of this
merry-go-round points
A. right. B. left.
C. up.
D. down.
E. into the screen.
F. out of the screen.
G. clockwise
H. counter-clockwise.
This hand-cranked flashlight is pointed
(mostly) out of the screen toward you.
The torque being applied to power it up
is in what direction?
A.clockwise
B. counterclockwise
C. forward (out of the screen)
D. left
E. right
Torques and the angular momentum
(spin) they produce are assigned
directions by the “Right Hand Rule.”
This wheel is rolling away from you
(into the screen):
Its angular
momentum
points in
what direction?
A. right. B. left.
C. down. D. up.
E. into the screen.
F. out of the screen.
The mass of Mars is 1/10 that of Earth,
and its radius is 1/2 that of Earth. What
is the acceleration of gravity on Mars?
(A)
(B)
(C)
(D)
(E)
0.1 g
0.2 g
0.4 g
0.5 g
0.8 g
The 90-kg fullback
runs up the middle
at 8 m/sec
straight into the
waiting arms of
the 110-kg
defensive tackle.
The tackle wraps his arms about the
fullback and the two are carried along
together by the fullback’s
momentum with what speed?
A.
B.
C.
D.
3.6 m/sec
5.4 m/sec
6.5 m/sec
7.2 m/sec
When stopped at the
top of a Ferris wheel,
the normal force
exerted by your seat is
equal to your weight.
How does the normal force supporting you
change as you glide rapidly past the top?
A) The normal force stays the same.
B) The normal force becomes smaller.
C) The normal force becomes larger.
You are at an amusement
park, taking a ride on the
Super Shot drop tower.
After lifting you
hundreds of feet in the
air, this ride simply drops
you. As you plummet,
(A) your constant momentum downward
gives you feeling a of weightless.
(B) though moving down you experience
a sense of velocity up.
(C) you are accelerating down at the
same rate as all your organs
giving a sensation of weightlessness.
(D) you are moving down at constant
velocity and therefore feel weightless.
Two different balloons
are inflated with air:
a rubber balloon and a
Mylar balloon.
The rubber expands as its pressure increases,
but the Mylar one cannot increase in volume.
If both are left out in the hot sun, the
upward buoyant force on the rubber
balloon will
(A) increase, but decrease for the Mylar balloon.
(B) remain the same, but decrease for the Mylar.
(C) increase, while it doesn’t change at all for
the Mylar balloon.
(D) increase, and also increase for the Mylar
balloon as well.
(E) decrease, while increasing for the Mylar.
(F) decrease, and also decrease for the Mylar.
Bullets strike
Superman in
the chest and
stomach! An
initial volley
catches him
unprepared,
but not the
second!!!!
Some bounce right back, while others
were stopped dead, dropping to the earth.
Which delivered the
greater force of impact?
A. the bounced bullets
B. the stopped bullets
C. both the same.
The center of gravity of each of the
trucks is shown by the black dot.
Which of the trucks will tip over?
1)
2)
3)
4)
5)
6)
A
B
C
A and C
all of them
none of them
A box is placed on a ramp in the
configurations shown below. Friction
prevents it from sliding. The center
of mass of the box is indicated by a
blue dot in each case.
In which cases does the box tip over
?
1
(a) all
3
2
(b) 2 & 3
(c) 3 only
Lecture 21: 20 Questions
Question:
1.
D
30 Newtons
2.
B
9 Joules.
3.
C
15 Newtons
4.
B
9 Joules
5.
D
9 Joules
6.
F
Circular motion  centr. F
7.
C
toward the pole
8.
C
accelerating to the left.
9.
B
a=v2/R  R= v2/a (a=9g) R=1020m.
10.
C
up
11.
E
right (use the thumb of your curled right hand)
12.
B
left
13.
C
4/10
14.
A
90(8)+0=(200)v
v=720/200
15.
B
smaller.
16.
C
accelerating down
17.
C
increases for rubber, no change for Mylar
18.
A
Bounced bullets=twice the impulse of stopped.
19.
A
Center of mass not over base.
20.
C
3 only.