Review Exercise 4-2
Chapter 6
Work and Energy
Provide definitions or appropriate response for questions 1 through 7 and circle
the correct answer for questions 8 through 13.
1.
Clearly state the work energy principle in words - do not use an
equation
The net
work done on an object is equal to the change in the object's kinetic
energy.
2. Clearly define a
conservative force in words - do not use an equation.
Forces for which the work done does not depend on the path taken but only
upon the initial and final positions.
3. List a conservative force:
_____________________
gravity
4. List a non-conservative
force: ________________________
friction
5. Clearly define total
mechanical energy of a system in words - do not use an equation.
It is the sum of the kinetic and potential energies at any moment.
6. What is the requirement for
the total mechanical energy of a system to be conserved?
When no non-conservative forces are acting - when only conservative forces
are acting.
7. Clearly define average power
in words - do not use an equation.
Average power is defined as th e work divided by the time to do it.
8. What is the correct unit of
work expressed in SI units?
A) kg m/s2
B) kg m2/s
C)
kg m2/s2
Answer: C
D) kg2 m/s2
9. What is the correct unit of
energy expressed in SI units?
A) kg m/s2
B) kg m2/s
Answer:
B
C) kg m2/s2
D) kg2 m/s2
10. A 70-N object was lifted
3.0 m vertically and is being held there.
How much work is being done in
holding the
box in this position?
A) more than
100 J
B)
100 J
C)
less than 100 J, but more than 0 J
D)
0 J
Answer: D
11. If you walk 10.0 m
horizontally forward at a constant velocity carrying a 5-N object, the
amount of
work you do is
A) more than 50
J.
B)
equal to 50 J
C)
less than 50 J, but more than 0 J.
D)
zero.
Ans: D
12. Does the centripetal force
acting on an object do work on the object?
A) Yes, since a
force acts and the object moves, and work is force times distance.
B) Yes, since
it takes energy to turn an object.
C) No, because
the object has constant speed.
D) No, because the force
and the displacement of the object are perpendicular.
Answer:
D
13. If the net work done on an
object is negative, then the object's kinetic energy
A) decreases.
Answer:
A
B)
remains the same
C) increases.
D)
is zero
Chapter 12
Sound
List the information required for question 1; circle the correct answer for
questions
2 through 6.
1.
The text discussed 3 aspects of sound in the introduction to the
chapter. One of these is a vibrating object. List
the other 2 below.
a._____________________________________________________________________________
b._____________________________________________________________________________
Energy
transferrred from source in form of longitudinal sound waves
Sound is
detected by ear or a microphone
2. Which of the following is a
false statement?
A) Sound
waves are longitudinal pressure waves.
B) Sound can
travel through a vacuum.
Answer:
B
C) Light
travels very much faster than sound.
D) The
transverse waves on a vibrating string are different from sound waves.
E) "Pitch"
(in music) and frequency have approximately the same meaning.
3. What determines "loudness"
of a musical note?
A) frequency
B)
velocity
C)
phase
D)
amplitude
Answer:
D
4. A sound source departs from
a stationary observer. The
frequency heard by the observer is
A) higher
than the source.
B) lower
than the source.
Answer:
B C)
the same as that of the source
5. You double your distance
from a sound source that is radiating equally in all directions.
What happens to
the intensity of the sound? It
reduces to
A) one-half
its original value.
C)
one-sixteenth its original value.
B)
one-fourth its original value.
Answer:
B
D)
none of these answers
6. Which of the following
increases as a sound becomes louder?
A) frequency
B)
wavelength
C)
amplitude
Answer:
C D)
period
E)
velocity
Chapter 22
Electromagnetic Waves
List information required for question 1 through 3; circle the correct
answer for questions
2 through 7.
1. Given that an electromagnetic wave travels north and its electric field is oscillating in a plane that is oriented in an East-West direction. Describe the direction of the
magnetic field
vector for this wave.
We know that, for an EM wave, the direction of travel, the magnetic field,
and the electric field are all perpendicular to each other.
We can view the situation on a flat surface as the wave going north and its
electric field as going horizontally (E-W) back and forth
The magnetic field, therefore, must be oscillating up and down.
2. Given that the wavelength of a wave is 1.0 cm, what is its
frequency? Give both a number and the correct
units for the answer.
We use the relationship c = fl
where c is the speed, f is the frequency, and
l
is the wavelength
f = c/l
= (3.00x108 m/s/1.0 x10-2 m) = 3.0 x 1010
Hz
3.
Maxwell's equations are the basic equations for all electromagnetism.
Three of them are based on works of
other pioneers. List these pioneers below.
a.
__________________________________
Coulomb's law or Gauss' law
b.
__________________________________
Ampere's law
c.
__________________________________
Faraday's law
4. An electric field is
produced by a
A)
constant magnetic field.
C)
either a constant or a changing magnetic field.
B)
changing magnetic field.
Answer:
B
D)
none of the given answers
5. An electromagnetic wave is
traveling to the east. At one
instant at a given point its E vector points straight up.
What is the direction of its B vector?
A) north
B)
down
C)
east
D)
south
Answer:
D
6. The strength of both the
electric and magnetic fields in the radiation field are found to decrease
with
distance as
A) 1/r.
Answer:
A
B)
1/r2
C)
1/r3
D)
1/r4.
7. Electromagnetic waves are
A)
longitudinal.
C)
both longitudinal and transverse.
B)
transverse. Answer:
B D) neither
longitudinal or transverse