Download Chapter 3 Section 3

Name
Date
Forces and Newton’s Laws
Section 3 Using Newton’s Laws
Skim through Section 3 of your book. Write three questions that
come to mind from reading the headings and the illustration
captions.
1. Accept all reasonable responses.
2.
3.
Review
Vocabulary Define momentum using a dictionary or your book.
momentum
property of a moving object that equals its mass times its
velocity
New
Vocabulary State the definitions of the terms below as found in your book.
air resistance
a friction-like force opposing the motion of objects that move
centripetal force
law of conservation of
momentum
a force exerted towards the center of a curved path
states that if a group of objects exerts forces only on each other,
their total momentum does not change
Academic Use a dictionary to define initial. Then use it as an adjective in a
Vocabulary sentence to show its scientific meaning.
initial
the first; Student responses will vary.
38 Forces and Newton’s Laws
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
through the air
Name
Date
Section 3 Using Newton’s Laws
What happens in
a crash?
I found this information
on page
.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
SE, p. 86
RE, p. 50
Newton’s Second
Law and
Gravitational
Acceleration
I found this information
on page
.
SE, p. 87
RE, p. 51
(continued)
Analyze the effects on a passenger riding in a car traveling at
50 km/h that collides head-on with a solid object.
Without Restraints
With Safety Belts and
Air Bags
Passenger continues moving
forward.
Passenger is slowed by the
safety belt.
Passenger slams into
dashboard, steering wheel, or
front seats.
Passenger is cushioned
by the air bag.
Passenger may be thrown
from the car.
Passenger stays in the car.
Analyze the formula W mg to explain how an object’s weight
can change even when its mass remains constant. Accept all
reasonable responses.
Even though m remains constant, g can change because it
represents the strength of local gravity. If g changes, then W
changes. On Earth, g is about 9.8 m/s2, but on the Moon it is 1/6
that. On a larger planet it is greater. In space, far away from
any planet or other large body, g is essentially zero and an object
has no weight at all, but its mass will not change.
Air Resistance
I found this information
on page
.
SE, pp. 87–88
RE, pp. 51–52
Contrast the terminal velocity of a parachutist with an open chute
to the terminal velocity of the same parachutist with a closed chute.
Accept all reasonable responses. The parachutist will have a
lower terminal velocity with the chute open than with it closed.
Because an open chute catches much more air than a closed one,
the air resistance needed to counteract the parachutist’s weight is
achieved at a much lower velocity with an open chute than with
a closed one.
Forces and Newton’s Laws 39
Name
Date
Section 3 Using Newton’s Laws
Weightlessness
and Free Fall
(continued)
Distinguish between an object that is truly weightless and an
object that is weightless because it is in free fall.
I found this information
on page
.
Accept all reasonable responses. True weightlessness requires the
SE, p. 89
RE, p. 52
total absence of gravity. Weightlessness in free fall is really just the
appearance of weightlessness due to the fact that, if the object were
placed on a scale during the free fall, the scale would read zero.
I found this information
on page
.
SE, p. 90
RE, p. 53
Force and
Momentum
I found this information
on page
.
SE, p. 91
RE, p. 54
Create a top view of an object
moving in a circle at constant speed,
such as a ball on a string. Show at
least two positions of the object. At
each position, draw an arrow for the
object’s velocity and another arrow
for the centripetal acceleration of the
object.
Velocity
Centripetal
acceleration
Velocity
Calculate the force that is needed to propel a rocket into space
if the rocket weighs 10,000 kg and the escape velocity for
Earth’s gravity is 11 km/s. (Hint: use the formula F ma).
Fill in the information below before calculating.
Mass
10,000 kg
Initial velocity
0 km/s
Final velocity
11 km/s
Time
10 minutes
Force
66,000,000 N
S UMMARIZE I T
laws of motion.
40 Forces and Newton’s Laws
After Reading this chapter, summarize Newton's three
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Centripetal
Forces
Name
Date
Tie It Together
Forces and Newton’s Laws
Combine some of what you have learned about forces in this chapter into
a picture of a wooden block sliding across a table. Use arrows to show the
following:
• As the block slides, friction with the table slows the block down.
• Gravity pulls the block downward.
• The force of gravity is balanced by an upward force exerted by the table
on the block.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Drawing should show friction as a horizontal arrow, gravity as a downward arrow, and the
force of the table on the block as an upward arrow. If the student also draws an arrow
showing the block’s motion, this should point in the opposite direction from the friction
force.
Suppose the block has a mass of 0.2 kg. Use W mg, with g 9.8 m/s 2,
to calculate the weight of the block.
W mg (0.20 kg)(9.8 m/s2) 1.96 N
The block continues to slide until it strikes a second block. Draw this event
below. Use arrows to show the following:
• During the collision, the first block exerts a force on second block which
causes the second block to move.
• The second block exerts an equal and opposite reaction force on the first
block, slowing it down.
The two forces should appear as horizontal arrows of equal length, pointing in
opposite directions.
Forces and Newton’s Laws 41
Name
Date
Forces and Newton’s Laws
Chapter Wrap-Up
In the left column, copy the questions you listed in the Chapter
Preview. In the right column, write down the answers you discovered
as you worked through the chapter.
W
What I wanted to find out
Accept all reasonable
responses.
L
What I learned
Check to make sure answers
to questions on left are correct.
Review
Review the information you included in your Foldable.
Study your Science Notebook on this chapter.
Study the definitions of vocabulary words.
Review daily homework assignments.
Re-read the chapter and review the charts, graphs, and illustrations.
Review the Self Check at the end of each section.
Look over the Chapter Review at the end of the chapter.
S UMMARIZE I T
learned about forces.
42 Forces and Newton’s Laws
After reading this chapter, list three things you have
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Use this checklist to help you study.