Chapter 12 Review

1
Chapter 12 Review
a
13 kg
b
d
c
A box is accelerated to the right across the
smooth surface of a table with an applied
force of 40 Newtons. The table surface provides a
friction coefficient of .2 Label the forces
and their values at letters A-D. Determine
the net force
C.O.F. x Normal F Friction 1 kg of mass 10
Newtons
2
Identify the forces at each colored arrow 5
forces total.
3
Question 1 Which way is the box moving? Question
2 Why is the Normal force arrow shorter than the
gravity arrow?
4
Chapter 12 Review

• Which of the following is a non-contact force?
• A) Friction
• B) Applied
• C) Gravity
• D) Normal

5
1 kilogram 10 newtons
How much force would be needed to lift the box
off of the table?
10 kg
6
What force will cause this diver to be propelled
off of the diving board? a) Tension b) Applied c)
Spring d) Normal
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Chapter 12 Review
Graph 1

Q Identify each type of graph. (what are they
showing) Q. Describe the motion of the
object in each graph and explain any changes in
that objects motion.
d (m)
T (sec)
Graph 2
V (m/s)
T (sec)
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Chapter 12 Review
Segment Distance Time Ave. Speed
A - B
B - C
C - D
A - D

Complete the table above with the correct values.
9
Chapter 12 Review

• Calculate the the acceleration between segments B
  - C
• How far did the object travel between segments A
  B?
• How many times did this object reach a constant
  speed?

10
Chapter 12 Review
a
Kevin applies a force of 150 Newtons to the
wooden crate and it does not move. What is the
exact name and magnitude in Newtons of the force
at letter B?
c
b
The second time, Kevin applies a force of 200
Newtons and the box slowly slides across the
floor. Is there still a force at letter B?
Explain If there is a force at letter b, how
could Kevin reduce that force?
b
11
Answers
Slide 1 Box on table   Forces  Gravity letter
C 127.4 N (13 kg x 9.8) F ma Normal Force
letter A 127.4 N (same as above) Applied
Force B 40 N Friction (kinetic) letter D
25.48 N (.2 x Normal F) Net Force 14.52 N
Right Acceleration 1.11 m/s/s Slide 2 Motion
Acceleration graphs   Graph 1 is a speed graph.
The motion shown is an object that starts out In
motion, stops for a short time and then resumes
its motion.   Graph 2 is an acceleration graph.
The object accelerates, then reaches a constant
speed, this is followed by negative acceleration,
and then the final segment shows the objet
accelerating positively again.
12
Answers
Slide 4 Acceleration   1. 3.3 m/s/s 2. 50
meters 3. 3 times
13
Answers
Slide 5 Friction forces   Diagram 1 Static
friction (150 N) is to Kevins applied force of
150 Newtons therefore the horizontal (sideways)
forces are equal, thus no acceleration.   Diagram
2 There is still a force present at letter b.
That force is now kinetic or sliding
friction. Since Kevin is applying greater force,
he overcomes static friction, but still has to
deal with the kinetic friction of the crate
against the floor. He could reduce this by
putting the crate on wheels. Rolling friction is
many times less than sliding friction.