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NAME ______________________________________ DATE _______________ CLASS ____________________
Section
HOLT PHYSICS
4-1 Diagram Skills
Changes in Motion
A large, square box of exercise equipment sits on a storeroom floor. A rope
is tied around the box. Assume that if the box moves along the floor, there
is a backward force that resists its motion.
1. Suppose that the box remains at rest. In the space provided, draw a free-
1.
body diagram for the box. Label each force involved in the diagram.
2. Suppose a warehouse worker moves the box by pulling the rope to the
2.
HRW material copyrighted under notice appearing earlier in this book.
right horizontal to the ground. In the space provided, draw a free-body
diagram for the box. Label each force involved in the diagram.
3. Suppose the warehouse worker moves the box by pulling the rope to the
3.
right at a 50° angle to the ground. In the space provided, draw a freebody diagram for the box. Label each force involved in the diagram.
Chapter 4
17
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Forces and the Laws of Motion
Chapter
4
Section 4-1, p. 17
1. The diagram should show two forces: 1) Fg (or mg)
pointing down; 2) an equal and opposite force of the
floor on the box pointing up.
2. The diagram should show four forces: 1) Fg (or mg)
pointing down; 2) an equal and opposite force of the
floor on the box pointing up; 3) F pointing to the right,
parallel to the ground; 4) Fresistance pointing to the left,
parallel to the ground.
3. The diagram should show four forces: 1) Fg (or mg)
pointing down; 2) F pointing to the right at a 50° angle
to the horizontal; 3) a force equal to Fg minus the vertical
component of the force F being applied at a 50° angle;
and 4) Fresistance to the left, parallel to the ground.
Section 4-2, p. 18
1. Fnet = F1 + F2 + F3 = 0
2. String 1: 0, −mg
4. F1 = 20.6 N
String 3: F3 cos q2 , F3 sin q2
3. Fx net = −F2 cos q1 + F3 cos q2 = 0
F2 = 10.3 N
Fy net =
−F2 sin q1 + F3 sin q2 + F1 = 0
F3 = 17.8 N
String 2: −F2 cos q1, F2 sin q1
Section 4-3, p. 19
1. Fs on b and Fb on s ; Fg on s and Fs on g; Ffr,1 and −Ffr,1;
Ffr,2 and −Ffr,2.
2. Fs on b, Fb on s , −Ffr,1
5. Fy,box = Fs on b − mg = 0
6. Fx,sled = Ma = F cos q − Ffr,1 − Ffr,2
3. Fg on s , Fs on g ; Fb on s , Ffr,1, F, Ffr,2
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4. Fx,box = ma = −Ffr,1
7. Fy,sled = Fg on s + F sin q − Fb on s − Mg = 0
III
Section 4-4, p. 20
1. 44 N
3. a. 21 N, up the ramp
2. 31 N
4. a. 18 N, down the ramp
b. yes
b. yes
Chapter 4 Mixed Review
1. a. at rest, moves to the left, hits back wall
b. m2 a
b. moves to the right (with velocity v), at rest, neither
c. F − m2 a = m1a
c. moves to the right, moves to the right, hits front wall
m1
d. 
F
m1 + m2
2. a. mg, down
b. mg, up
c. no
d. yes
F
3. a. a = 
m1 + m2
F − Fk
4. a. a = 
m1 + m2
b. m2 a − Fk
c. F − m2 a − Fk = m1a − Fk
m1
d. 
(F − Fk)
m1 + m2
Section Three—Section Review Worksheet Answers
III–5