Assumption College English Program
Mr. Stephen Dobosh’s
E P - M 4 P h y s i c s C l a s s w o r k / H o m e w o r k P a c k e t
Chapter 4: Forces and the Laws of Motion
Section 1: Changes in Motion
Section 2: Newton’s First Law
Section 3: Newton’s Second and Third Laws
Section 4: Everyday Forces
Student’s Name ……………………..…………………..…… EP-M …./…. ID #………….. Register #……
Much of the material within this packet is drawn from the course textbook Holt Physics that each of you have purchased. This content is copyrighted © 2012 by Holt McDougal, a division of Houghton Mifflin Harcourt Publishing Company. No part of this work may be
reproduced or transmitted in any form without prior written permission of the copyright owner.
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 2 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
THIS PAGE INTENTIONALLY LEFT BLANK
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 3 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
EQUATION SHEET
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 4 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
THIS PAGE INTENTIONALLY LEFT BLANK
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 5 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
In-Class Free-Body Diagram Practice
1. An acrobat is suspended motionless from the ceiling by a rope. Fr
ee-B
od
y D
iagr
am
2. An egg is free-falling from a nest in a tree. Neglect air resistance.
Free
-Bo
dy
Dia
gram
3. An egg is falling (not freely, do not neglect air resistance) from a nest in a tree.
Free
-Bo
dy
Dia
gram
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 6 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
5. A rightward force is applied to a book in order to move it across a desk with a rightward acceleration. Consider frictional forces. Neglect air resistance.
Free
-Bo
dy
Dia
gram
6. A rightward force is applied to a book in order to move it across a desk at constant velocity. Consider frictional forces. Neglect air resistance.
Free
-Bo
dy
Dia
gram
7. A Bangkok taxi is (actually) stopping at a red light.
Free
-Bo
dy
Dia
gram
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 7 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
8. A skydiver is descending with a constant velocity. Of course, consider air resistance.
Free
-Bo
dy
Dia
gram
9. A car is parked on a sloped street.
Free
-Bo
dy
Dia
gram
10. A hot air balloon is accelerating upward.
Free
-Bo
dy
Dia
gram
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 8 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
11. A car is coasting to the right and slowing down.
Free
-Bo
dy
Dia
gram
12. A soccer ball while being kicked at a 45° angle.
Situ
atio
nal
Dia
gram
Free
-Bo
dy
Dia
gram
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 9 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
13. A soccer ball that has already been kicked at a 45° angle.
Situ
atio
nal
Dia
gram
Free
-Bo
dy
Dia
gram
14. A race car crashing head-on into a brick wall.
Situ
atio
nal
Dia
gram
Free
-Bo
dy
Dia
gram
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 10 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
THIS PAGE INTENTIONALLY LEFT BLANK
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 11 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
Chapter 4.1: Changes in Motion (pp. 118-122)
Practice A, pp. 121-122 #1-2
Drawing Free-Body Diagrams
Due: _________________
1. A truck pulls a trailer on a flat stretch of road. The forces acting on the trailer are the force
due to gravity (250 000 N downward), the force exerted by the cable connecting the trailer
to the truck (20 000 N to the right). The forces acting on the truck are the force due to
gravity (80 000 N downward), the force exerted by the road (80 000 N upward), the force
exerted by the cable (20 000 N to the left), and the force causing the truck to move forward
26 400 N to the right).
a. Draw and label a free-body diagram of the trailer.
b. Draw and label a free-body diagram of the truck.
2. A physics book is at rest on a desk. Gravitational force pulls the book down. The desk exerts
an upward force on the book that is equal in magnitude to the gravitational force. Draw a
free-body diagram of the book.
Note: You can draw one, single
diagram of both if you like.
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 12 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
Chapter 4.1: Changes in Motion (pp. 118-122)
Formative Assessment 4.1, p. 122 #1-6
Due: _________________
1. List three examples of each of the following:
a. a force causing an object to start moving
b. a force causing an object to stop moving
c. a force causing an object to change its direction of motion
2. Give two examples of field forces described in this section and two examples of contact
forces you observe in everyday life. Explain why you think that these are forces.
3. What is the SI unit of force? What is this unit equivalent to in terms of fundamental units?
4. Why is force a vector quantity?
5. Draw a free-body diagram of a football being kicked. Assume that the only forces acting on
the ball are the force due to gravity and the force exerted by the kicker.
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 13 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
6. Interpreting Graphics Study the force diagram shown (Holt 2009 ed., Figure 3(a)). Redraw
the diagram, and label each vector arrow with a description of the force. In each description,
include the object exerting the force and the object on which the force is acting.
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 14 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
Chapter 4.2: Newton’s First Law (pp. 123-127)
Practice B, pp. 125-126 #1-3
Determining Net Force
Due: _________________
1. A man is pulling on his dog with a force of 70.0 N directed at an angle of +30.0° to the
horizontal. Find the x and y components of this force.
2. A gust of wind blows an apple from a tree. As the apple falls, the gravitational force on the
apple is 2.25 N downward, and the force of the wind on the apple is 1.05 N to the right. Find
the magnitude and direction of the net force on the apple.
3. The wind exerts a force of 452 N north on a sailboat, while the water exerts a force of 325 N
west on the sailboat. Find the magnitude and direction of the net force on the sailboat.
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 15 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
Chapter 4.2: Newton’s First Law (pp. 123-127)
Formative Assessment 4.2, p. 127 #1-5
Due: _________________
1. If a car is traveling westward with a constant velocity of 20 m/s, what is the net force acting
on the car?
2. If a car is accelerating downhill under a net force of 3674 N, what additional force would
cause the car to have a constant velocity?
3. The sensor in the torso of a crash-test dummy records the magnitude and direction of the
net force acting on the dummy. If the dummy is thrown forward with a force of 130.0 N
while simultaneously being hit from the side with a force of 4500.0 N, what force will the
sensor report?
4. What force will the seat belt have to exert on the dummy in item 3 to hold the dummy in the
seat?
5. Critical Thinking Can an object be in equilibrium if only one force acts on the object?
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 16 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
Chapter 4.3: Newton’s Second and Third Laws (pp. 128-132)
Practice C, pp. 129-130 #1-5
Newton’s Second Law
Due: _________________
1. The net force on the propeller of a 3.2 kg model airplane is 7.0 N forward. What is the
acceleration of the airplane?
2. The net force on a golf cart is 390 N north. If the cart has a total mass of 270 kg, what are the
magnitude and direction of the cart’s acceleration?
3. A car has a mass of 1.50 × 103 kg. If the force acting on the car is 6.75 × 103 N to the east,
what is the car’s acceleration?
4. A soccer ball kicked with a force of 13.5 N accelerates at 6.5 m/s2 to the right. What is the
mass of the ball?
5. A 2.0 kg otter starts from rest at the top of a muddy incline 85 cm long and slides down to
the bottom in 0.50 s. What net force acts on the otter along the incline?
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 17 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
Chapter 4.3: Newton’s Second and Third Laws (pp. 128-132)
Formative Assessment 4.3, p. 132 #1-5
Due: _________________
1. A 6.0 kg object undergoes an acceleration of 2.0 m/s2.
a. What is the magnitude of the net force acting on the object?
b. If this same force is applied to a 4.0 kg object, what acceleration is produced?
2. A child causes a wagon to accelerate by pulling it with a horizontal force. Newton’s third law
says that the wagon exerts an equal and opposite force on the child. How can the wagon
accelerate? (Hint: Draw a free-body diagram for each object.)
3. Identify the action-reaction pairs in the following situations:
a. A person takes a step.
b. A snowball hits someone in the back.
c. A baseball player catches a ball.
d. A gust of wind strikes a window.
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 18 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
4. The forces acting on a sailboat are 390 N north and 180 N east. If the boat (including crew)
has a mass of 270 kg, what are the magnitude and direction of the boat’s acceleration?
5. Critical Thinking If a small sports car collides head-on with a massive truck, which vehicle
experiences the greater impact force? Which vehicle experiences the greater acceleration?
Explain your answers.
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 19 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
Chapter 4.4: Everyday Forces (pp. 133-141)
Practice D, p. 137 #1-3
Coefficients of Friction
Due: _________________
1. Once the crate in Sample Problem D is in motion, a horizontal force of 53 N keeps the crate
moving with a constant velocity. Find µk, the coefficient of kinetic friction, between the crate
and the floor.
2. A 25 kg chair initially at rest on a horizontal floor requires a 165 N horizontal force to set it in
motion. Once the chair is in motion, a 127 N horizontal force keeps it moving at a constant
velocity.
a. Find the coefficient of static friction between the chair and the floor.
b. Find the coefficient of kinetic friction between the chair and the floor.
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 20 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
3. A museum curator moves artifacts into place on various different display surfaces. Use the
values in Figure 4.7 (Holt 2009 ed., Table 2) to find Fs,max and Fk for the following situations:
a. moving a 145 kg aluminum sculpture across a horizontal steel platform
b. pulling a 15 kg steel sword across a horizontal steel shield
c. pushing a 250 kg wood bed on a horizontal wood floor
d. sliding a 0.55 kg glass amulet on a horizontal glass display case
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 21 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
Chapter 4.4: Everyday Forces (pp. 133-141)
Practice E, p. 138-139 #1-4
Overcoming Friction
Due: _________________
1. A student pulls on a rope attached to a box of books and moves the box down the hall. The
student pulls with a force of 185 N at an angle of 25.0° above the horizontal. The box has a
mass of 35.0 kg, and µk between the box and the floor is 0.27. Find the acceleration of the
box.
2. The student in item 1 moves the box up a ramp inclined at 12° with the horizontal. If the box
starts from rest at the bottom of the ramp and is pulled at an angle of 25.0° with respect to
the incline and with the same 185 N force, what is the acceleration up the ramp? Assume
that µk = 0.27.
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 22 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
3. A 75 kg box slides down a 25.0° ramp with an acceleration of 3.60 m/s2.
a. Find µk between the box and the ramp.
b. What acceleration would a 175 kg box have on this ramp?
4. A box of books weighing 325 N moves at a constant velocity across the floor when the box is
pushed with a force of 425 N exerted downward at an angle of 35.2° below the horizontal.
Find µk between the box and the floor.
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 23 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
Chapter 4.4: Everyday Forces (pp. 133-141)
Formative Assessment 4.4, p. 141 #1-5
Due: _________________
1. Draw a free-body diagram for each of the following objects:
a. a projectile accelerating downward in the presence of air resistance
b. a crate being pushed across a flat surface at a constant speed
2. A bag of sugar has a mass of 2.26 kg.
a. What is its weight in newtons on the moon, where the acceleration due to gravity is
one-sixth that on Earth?
b. What is its weight on Jupiter, where the acceleration due to gravity is 2.64 times
that on Earth?
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 24 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
3. A 2.0 kg block on an incline at a 60.0° angle is held in equilibrium by a horizontal force.
a. Determine the magnitude of this horizontal force. (Disregard friction.)
b. Determine the magnitude of the normal force on the block.
4. A 55 kg ice skater is at rest on a flat skating rink. A 198 N horizontal force is needed to set
the skater in motion. However, after the skater is in motion, a horizontal force of 175 N
keeps the skater moving at a constant velocity. Find the coefficients of static and kinetic
friction between the skates and the ice.
5. Critical Thinking The force of air resistance acting on a certain falling object is roughly
proportional to the square of the object’s velocity and is directed upward. If the object falls
fast enough, will the force of air resistance eventually exceed the weight of the object and
cause the object to move upward? Explain.
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 25 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
Chapter 4 Review (pp. 143-147)
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 26 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 27 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 28 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 29 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 30 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 31 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].
Chapter 4: Forces and the Laws of Motion Classwork/Homework Packet
Mr. Stephen Dobosh Page 32 of 32
Questions? Come see Mr. Steve or email him with a picture of your work at [email protected].