Transcript Chapter 1 - asmasaid

Physics of Everyday Phenomena
W. Thomas Griffith
Juliet W. Brosing
Chapter 8
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Question 8.1
Which of the following is NOT a unit for
rotational displacement?
A) Degrees
B) Rad/s
C) Revolutions
D) radians
Question 8.2
Which of the following is a unit for rotational
velocity?
A) hours/radians
B) Radians
C) Rev/sec
D) degrees
Question 8.3
A CD makes one complete revolution every
tenth of a second. The angular velocity of
point 4 is:
A) the same as for pt 1.
B) twice that of pt 2.
C) half that of pt 2.
D) 1/4 that of pt 1.
E) four times that of pt 1.
Question 8.4
A CD makes one complete revolution every
tenth of a second. Which has the largest
linear (tangential) velocity?
A) point 1
B) point 2
C) point 3
D) point 4
Question 8.5
Which object has the largest magnitude of
rotational acceleration?
A) An object starting from rest and reaching 2
rev/s in 20 sec
B) An object rotating at 3 rev/s and coming to
a stop in 10 sec
C) An object rotating at a constant 4 rev/s
Question 8.6
When using the equation that relates linear
speed and rotational velocity (v = r) what
are acceptable units for the rotational
velocity () ?
A) degrees/s
B) Radians/min
C) Rev/min (rpm)
Question 8.7
If two children sit on a seesaw and one is twice
as heavy as the other, in order to achieve
balance the lighter child must sit
A) half as far from the fulcrum
B) twice as far from the fulcrum
C) the same distance from the fulcrum
D) four times as far from the fulcrum
Question 8.8
To increase the applied torque one can
A)
B)
C)
D)
E)
Increase the force
Increase the lever arm by moving to the end of the
lever
Increase the lever arm by applying the force
perpendicularly to the lever
All of the above
None of the above
Question 8.9
The point in or near an object about which the
weight of the object itself exerts no net
torque is the
A) impulse point
B) fulcrum
C) center of gravity
Question 8.10
If the distance between a point mass and the
pivot point is tripled, the rotational inertia
of the object about that point is multiplied by
A) 9
B) 3
C) 1/3
D) 1/9
Question 8.11
Which rod has the smallest rotational inertia, I, the one
rotating about the end, or the one rotating about the
center?
A) Rotating about end
B) Rotating through
center
C) They both have the
same I, since they
have the same mass
and length
Question 8.12
Two objects, a ring and a disk, both with equal mass
and radii. Each is rotating about an axis through its
center, as shown. Which has the greatest rotational
inertia, I, a uniform disk or a ring?
A) They have the same I, since they both
have the same mass and radius
B) The disk
C) The ring
Question 8.13
Which will win the race to the bottom of the
incline: a hoop, or a disk with the same
mass and radius?
A) the hoop
B) the disk
C) they will both reach the bottom at the
same time
Question 8.14
Angular momentum is calculated as the
A) product of mass times velocity
B) product of mass times angular velocity
C) product of moment of inertia times
velocity
D) product of moment of inertia times
angular velocity
Question 8.15
Angular momentum is conserved
A) only when the net force acting on the
system is zero
B) only when the angular velocity is zero
C) only when the net torque acting on the
system is zero
D) in all cases
Question 8.16
A figure skater spins with her arms extended.
When she pulls in her arms, she spins faster
because
A) she has decreased her rotational inertia.
B) she has increased her rotational inertia.
C) she has increased her angular
momentum.
D) the ice exerts a torque on her skates.
Question 8.17
Meredith sits in the middle of a merry-go-round
that her brother Kiel is pushing. If
Meredith moves to the outer edge of the
merry-go-round, it will
A) speed up.
B) slow down.
C) spin at the same rate.
Question 8.18
What is the direction of the angular momentum
vector for a wheel spinning as shown
below?
A) Upward
B) Downward
C) Clockwise
D) Counterclockwise
Question 8.19
As we learned in Chapter 5, the gravitational
force between the earth and the sun
supplies the centripetal force which causes
the Earth to rotate about the sun. Does this
force produce a torque about the sun?
A) No
B) Yes
Question 8.20
As a planet moves closer to the sun in its
elliptical orbit its rotational velocity
increases. Is angular momentum
conserved?
A) Yes
B) No
Question 8.21
When angular momentum is conserved
A) The magnitude of the total angular
momentum remains constant
B) The direction of the total angular
momentum remains constant
C) The magnitude and direction of the total
angular momentum remains constant
Answer Key to Chapter 8
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
B
C
A
D
B
B
A
D
C
A
B
12)
13)
14)
15)
16)
17)
18)
19)
20)
21)
C
B
D
C
A
B
A
A
A
C