Physics 101
Homework 3
Due September 3
1. A stone is dropped from the top of a cliff. It hits the ground below after 3.25 s. How high is
the cliff?
Solution:
Choose upward to be the positive direction, and take y = 0 at the bottom of the cliff. The initia
Physics 101
Homework 8
Due September 22
1. Two railroad cars, each of mass 7650 kg and traveling 95 km h in opposite
directions, collide head-on and come to rest. How much thermal energy is produced in
this collision?
Solution:
Use conservation of energy,
Physics 101
Homework 13
Due October 15
1. The specific heat of water is quite large. Explain why this fact makes water particularly good
for heating systems (that is, hot-water radiators).
Solution:
Because the specific heat of water is quite large, it ca
Physics 101
Homework 10
Due October 6
1. The musical note A4 has a frequency of 440 Hz. Calculate the period and the angular
frequency.
Solution:
T
1
1
0.0023s ; 2f 2 440 Hz 2764 s 1
f
440 Hz
2. A pendulums length is 1.0 m. Calculate frequency, period an
Homework 19
Physics 101
Due November 4
Due November 5
1. What kind of change on the emf induced in the coil is produces if the number of loops of
wire in a coil is increased 10 times, assuming all other factors remain constant?
Solution:
Faradays law:
. S
Physics 101
Homework 18
Due November 3
1. A vertical straight wire carrying an upward 24-A current exerts an attractive force per unit
length of
on a second parallel wire 7.0 cm away. What current (magnitude and
8.8 10 4 N m
direction) flows in the second
Homework 16
Due October 27
Physics 101
1. A current of 3.2 A flows in a wire. How many electrons are flowing past any point in the wire
per second?
Solution:
Use the definition of current:
Q
1.30 C 1 electron
I
1.30 A
8.13 1018 electrons s
t
s
1.60 10
Physics 101
Homework 20
Due November 17
1. An electromagnetic wave in vacuum is moving in +x direction. At time t=0 and at the
position (x,y,z)=(0,0,0), the magnetic field is pointing in the +z direction. In what direction
is pointing the electric field a
Physics 101
Homework 21
Due November 19
Name
#_
(You must show your work or explain your answers to get full credit, simply writing a
numerical answer is not sufficient. You can type your solutions on this file, or write them on a
separate page, or you ca
Physics 101
Exam 1
Spring 2015
1. Calculate: 5 4 =
A) 1
B) 2
C) 3
D) 4
E) 5
2. What statement is correct?
A)
B)
C)
D)
E)
Instantaneous speed can be equal to average speed
Instantaneous speed cannot be bigger than average speed
Instantaneous speed cannot b
Homework 17
Due October 29
Physics 101
1. (a) Determine the resistance of, and current through, a 75-W lightbulb connected to its proper
source voltage of 120 V. (b) Repeat for a 440-W bulb.
Solution:
(a)
P
V2
R
R
P IV I
V2
P
P
V
P
R
R
P IV I
2. The e
Homework 15
Due October 22
Physics 101
1. If a positive charge is initially at rest in an electric field, will it move toward a region
of higher potential or lower potential? What about a negative charge? How does the
potential energy of the charge change
Physics 101
Homework 2
Due September 1
1. Can an object have a varying speed if its velocity is constant? If yes, give examples.
Solution:
By definition, if an object has a constant velocity, then both the object's speed and its
direction of motion are co
Physics 101
Homework 4
Due September 8
1. The force of gravity on a 2-kg rock is twice as great as that on a 1-kg rock. Why then doesnt
the heavier rock fall faster?
Solution: The acceleration of both rocks is found by dividing their weight (the force of
Physics 101
Homework 5
Due September 10
1. What is the maximum acceleration a car can undergo if the coefficient of static friction
between the tires and the ground is 0.80?
Solution:
A free-body diagram for the accelerating car is shown. The car does not
Physics 101
Homework 6
Due September 15
1. Suppose a car moves at constant speed along a hilly road. Where does the car exert the
greatest and least forces on the road: (a) at the top of a hill, (b) at a dip between two hills, (c)
on a horizontal road?
So
Physics 101
Homework 7
Due February 5
A box of mass 5.0 kg is accelerated from rest by a force across a floor at a rate of
7.0 s. Find the net work done on the box.
2.0 m s 2
for
Solution:
Since the acceleration of the box is constant, we can find the dis
Physics 101
Homework 9
Due September 24
1. A ball of mass 0.440 kg moving east ( x direction) with a speed of 3.30 m s collides
head-on with a 0.220-kg ball at rest. If the collision is perfectly elastic, what will be the speed
and direction of each ball
Physics 101
Homework 11
Due October 8
1. The predominant frequency of a certain fire engines siren is 1550 Hz when at rest. What
frequency do you detect if you move with a speed of 30.0 m s (a) toward the fire engine,
and (b) away from it?
Solution:
(a)
(
Homework 12
Physics 101
Due October 13
1. An ice cube floats in a glass of water filled to the brim. (a) What can you say about the
density of ice? (b)As the ice melts, will the glass overflow? Explain.
Solution:
(a) Since the ice floats, the density of i
Physics 101
Homework 14
Due October 20
1. How many electrons make up a charge of
30 .0 C?
Solution:
Use the charge per electron to find the number of electrons.
1 electron
14
30.0 106 C
1.87 10 electrons
19
1.602 10 C
2. What is the magnitude of th
Physics 101
Homework 12
Due October 14
Name
#_
(You must show your work or explain your answers to get full credit, simply writing a
numerical answer is not sufficient. You can type your solutions on this file, or write them on a
separate page, or you can