Transcript Living Things - Fairfield-Suisun Unified School District

Chapter 10 Forces
Table of Contents
Chapter Preview
10.1 The Nature of Force
10.2 Friction, Gravity, and Elastic Forces
10.3 Newton’s First and Second Laws
10.4 Newton’s Third Law
10.5 Rockets and Satellites
Chapter 10 Forces
Chapter Preview Questions
1. How do you know an object is in motion?
a. It has inertia.
b. It has mass.
c. It is changing position.
d. It has a reference point.
Chapter 10 Forces
Chapter Preview Questions
1. How do you know an object is in motion?
a. It has inertia.
b. It has mass.
c. It is changing position.
d. It has a reference point.
Chapter 10 Forces
Chapter Preview Questions
2. What is velocity?
a. speed
b. speed in a given direction
c. miles per hour
d. change in speed over time
Chapter 10 Forces
Chapter Preview Questions
2. What is velocity?
a. speed
b. speed in a given direction
c. miles per hour
d. change in speed over time
Chapter 10 Forces
Chapter Preview Questions
3. Which is the best definition of acceleration?
a. change in velocity
b. change in reference point
c. increase in speed
d. decrease in speed
Chapter 10 Forces
Chapter Preview Questions
3. Which is the best definition of acceleration?
a. change in velocity
b. change in reference point
c. increase in speed
d. decrease in speed
Chapter 10 Forces
Chapter Preview Questions
4. If an object starts out at rest and accelerates to 100 m/s,
what is its initial speed?
a. -100 m/s
b. 0 m/s
c. 100 m/s
d. 32 m/s
Chapter 10 Forces
Chapter Preview Questions
4. If an object starts out at rest and accelerates to 100 m/s,
what is its initial speed?
a. -100 m/s
b. 0 m/s
c. 100 m/s
d. 32 m/s
Chapter 10 Forces
What causes an object’s velocity to change?
You drop a tennis ball and
a baseball at the same
time. Why do the balls fall
to the floor?
Chapter 10 Forces
Latin Word Origins
Latin Origin
centri-
Meaning
Key Term
Center
Centripetal force
Chapter 10 Forces
Latin Word Origins
Latin Origin
com-
Meaning
Key Term
Together, with
Compression
Chapter 10 Forces
Latin Word Origins
Latin Origin
jacere
Meaning
Key Term
Throw
Projectile
Chapter 10 Forces
Latin Word Origins
Latin Origin
premere
Meaning
Key Term
Press
Compression
Chapter 10 Forces
Latin Word Origins
Latin Origin
pro-
Meaning
Key Term
Forward, before
Projectile
Chapter 10 Forces
Latin Word Origins
Latin Origin
tensus
Meaning
Key Term
Stretch
Tension
Chapter 10 Forces
Apply It!
Look at pro- and jacere and predict the meaning of projectile.
Revise your definition as needed as you read the chapter.
Look for words with these Latin origins as you read the chapter.
Sample: I see that pro- means “forward” and that jacere means “to throw.”
By combining the two I get the definition of projectile.
Chapter 10 Forces
End of Chapter
Preview
Chapter 10 Forces
Section 1:
The Nature of Force
How is a force described?
How do balanced and unbalanced forces affect
an object’s velocity?
Chapter 10 Forces
Combining Force Vectors
The strength and direction of the individual forces determine
the net force.
Chapter 10 Forces
Unbalanced Forces
Unbalanced forces acting on an object result in a net force
and cause a change in the object’s velocity.
Chapter 10 Forces
Balanced Forces
Balanced forces acting on an object do not change the
object’s velocity.
Chapter 10 Forces
Links on Force
Click the SciLinks button for links on force.
Chapter 10 Forces
End of Section:
The Nature of Force
Chapter 10 Forces
Section 2:
Friction, Gravity, and
Elastic Forces
What factors determine the strength of the friction force
between two surfaces?
What factors affect the gravitational force between two
objects?
Why do objects accelerate during free fall?
When is matter considered to be elastic?
Chapter 10 Forces
Gravity Between Objects
The force of gravity between objects increases with greater
mass and decreases with greater distance.
Chapter 10 Forces
Mass and Weight
The gravitational force exerted on a person or object at the
surface of a planet is known as weight.
Chapter 10 Forces
Free Fall
The graph shows how the speed
of an object in free fall changes
with time. Use the graph to
answer the following questions.
Chapter 10 Forces
Free Fall
Interpreting Graphs:
What is the speed of the
object at 1 second? At 3
seconds?
9.8 m/s; 29.4 m/s.
Chapter 10 Forces
Free Fall
Calculating:
Calculate the slope of the
graph. What does this
number represent?
The slope is 9.8. The speed
increases by 9.8 m/s each
second.
Chapter 10 Forces
Free Fall
Predicting:
Use the slope that you
calculated in Step 2 to predict
the object’s speed at 6
seconds.
58.8 m/s
Chapter 10 Forces
Free Fall
Drawing Conclusions:
The graph has a constant
slope. What does the slope
tell you about the object’s
motion?
The object’s speed increases
at a constant rate.
Chapter 10 Forces
Air Resistance
Falling objects with a greater surface area experience more
air resistance.
Chapter 10 Forces
Links on Friction
Click the SciLinks button for links on friction.
Chapter 10 Forces
Free Fall
Click the Video button to watch a movie about free fall.
Chapter 10 Forces
End of Section:
Friction, Gravity, and
Elastic Forces
Chapter 10 Forces
Section 3:
Newton’s First and
Second Laws
What is Newton’s first law of motion?
What is Newton’s second law of motion?
Chapter 10 Forces
Calculating Force
A speedboat pulls a 55-kg water-skier. The skier to accelerates at
2.0 m/s2. Calculate the net force that causes this acceleration.
Read and Understand
What information have you been given?
Mass of the water-skier (m) = 55 kg
Acceleration of the water-skier (a) = 2.0 m/s2
Chapter 10 Forces
Calculating Force
A speedboat pulls a 55-kg water-skier. The skier accelerates at 2.0 m/s2.
Calculate the net force that causes this acceleration.
Plan and Solve
What quantity are you trying to calculate?
The net force (Fnet) = __
What formula contains the given quantities and the unknown
quantity?
a = Fnet/m or Fnet = m x a
Perform the calculation.
Fnet = m x a = 55 kg x 2.0 m/s2
F = 110 kg • m/s2
F = 110 N
Chapter 10 Forces
Calculating Force
A speedboat pulls a 55-kg water-skier. The skier accelerates at 2.0 m/s2.
Calculate the net force that causes this acceleration.
Look Back and Check
Does your answer make sense?
A net force of 110 N is required. This does not include the force that
overcomes friction.
Chapter 10 Forces
Calculating Force
Practice Problem
What is the net force on a 1,000-kg object accelerating
at 3 m/s2?
3,000 N (1,000 kg x 3 m/s2)
Chapter 10 Forces
Calculating Force
Practice Problem
What net force is needed to accelerate a 25-kg cart
at 14 m/s2?
350 N (25 kg x 14 m/s2)
Chapter 10 Forces
More on Newton’s Laws
Click the PHSchool.com button for an activity
about Newton’s laws.
Chapter 10 Forces
End of Section:
Newton’s First and
Second Laws
Chapter 10 Forces
Section 4:
Newton’s Third Law
What is Newton’s third law of motion?
How can you calculate the momentum of an object?
What is the law of conservation of momentum?
Chapter 10 Forces
Newton’s Third Law of Motion
Newton’s third law of motion states that if one object exerts a
force on another object, then the second object exerts a force
of equal strength in the opposite direction on the first object.
Chapter 10 Forces
Calculating Momentum
Which has more momentum: a 3.0-kg sledgehammer swung at 1.5
m/s, or a 4.0-kg sledgehammer swung at 0.9 m/s?
Read and Understand
What information are you given?
Mass of smaller sledgehammer = 3.0 kg
Velocity of smaller sledgehammer = 1.5 m/s
Mass of larger sledgehammer = 4.0 kg
Velocity of larger sledgehammer = 0.9 m/s
Chapter 10 Forces
Calculating Momentum
Which has more momentum: a 3.0-kg sledgehammer swung at 1.5
m/s or a 4.0-kg sledgehammer swung at 0.9 m/s?
Plan and Solve
What quantities are you trying to calculate?
The momentum of each sledgehammer = __
What formula contains the given quantities and the unknown
quantity?
Momentum = Mass x Velocity
Perform the calculation.
Smaller sledgehammer = 3.0 km x 1.5 m/s = 4.5 kg•m/s
Larger sledgehammer = 4.0 km x 0.9 m/s = 3.6 kg•m/s
Chapter 10 Forces
Calculating Momentum
Which has more momentum: a 3.0-kg sledgehammer swung at 1.5
m/s or a 4.0-kg sledgehammer swung at 0.9 m/s?
Look Back and Check
Does your answer make sense?
It is possible for the 3.0-kg hammer to have more momentum than
the 4.0-kg one because it has a greater velocity.
Chapter 10 Forces
Calculating Momentum
Practice Problem
A golf ball travels at 16 m/s, while a baseball moves at 7
m/s. The mass of the golf ball is 0.045 kg and the mass
of the baseball is 0.14 kg. Which has greater
momentum?
Golf ball: 0.045 kg x 16 m/s = 0.72 kg•m/s
Baseball: 0.14 kg x 7 m/s = 0.98 kg•m/s
The baseball has greater momentum.
Chapter 10 Forces
Calculating Momentum
Practice Problem
What is the momentum of a bird with a mass of 0.018 kg
flying at 15 m/s?
0.27 kg•m/s (0.018 kg x 15 m/s = 0.27 kg•m/s)
Chapter-10 Forces
Conservation of Momentum
In the absence of friction, momentum is conserved when two
train cars collide.
Chapter 10 Forces
Momentum Activity
Click the Active Art button to open a browser window and
access Active Art about momentum.
Chapter 10 Forces
End of Section:
Newton’s Third Law
Chapter 10 Forces
Section 5:
Rockets and Satellites
How does a rocket lift off the ground?
What keeps a satellite in orbit?
Chapter 10 Forces
What Is a Satellite?
A projectile follows a curved path. The horizontal and vertical
motions act independently.
Chapter 10 Forces
What Is a Satellite?
The faster a projectile is thrown, the father it travels before it
hits the ground. A projectile with enough velocity moves in a
circular orbit.
Chapter 10 Forces
What Is a Satellite?
Depending on their uses, artificial satellites orbit at different
heights.
Chapter 10 Forces
End of Section:
Rockets and Satellites
Chapter 10 Forces
QuickTake Quiz
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