9 momentum and its conservation - poulin's...

9 Momentum and Its ConservationBIGIDEAWrite the Big Idea for this chapter.

Use the “What I Know” column to list the things you know about the Big Idea. Then list the questions you have about the Big Idea in the “What I Want to Find Out” column. As you read the chapter, fill in the “What I Learned” column.

KWhat I Know

WWhat I Want to Find Out

LWhat I Learned

Science Notebook • Momentum and Its Conservation 135

Program: TX HS Science Component: PPP SCI NTBKPRINTER PDF

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135_148_PPP_SN_C09_666028.indd 135135_148_PPP_SN_C09_666028.indd 135 06/05/13 3:15 PM06/05/13 3:15 PM

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MAIN IDEAWrite the Main Idea for this section.

Recall and write the definition of the Review Vocabulary term.

angular velocity

Use your book to fill in the term that matches its definition.

The product of the average net force on an object and the time interval over which it acts

The product of the object’s mass (m) and the object’s velocity (v)

States that the impulse on an object is equal to the change in its momentum

The product of a rotating object’s moment of inertia and angular velocity

States that an angular impulse on an object is equal to the change in the object’s angular momentum

Complete the diagram to identify two ways to write the equation for impulse.

9 Momentum and Its Conservation 1 Impulse and Momentum

REVIEW VOCABULARY

angular velocity

NEW VOCABULARY

FΔt

in terms ofvelocity

in terms ofmomentum

Student Edition, pp. 236–237

6(C)





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-Hill Education. Perm

ission is granted to reproduce for classroom use.

1 Impulse and Momentum (continued)

Impulse-Momentum Theorem

relates

and

and

change in

which is the product of

and and

on an object

which is the product of

Impulse

Its direction

How it is determined from a force-time graph


Use with Example Problem 1

Use this column for

scratch work and

sketches.

Describe the Impulse-Momentum Theorem by completing the diagram.

Write a sentence about each of the following properties of an impulse.

TRY IT !Problem

A skateboarder traveling at 4.45 m/s can be stopped by a strong force in 1.8 s and by a weak force in 5.3 s. The mass of the skateboarder and the skateboard is 56.3 kg. What is the impulse on the skateboarder? What is the average force on the skateboarder in each of these stops?

1. ANALYZE AND SKETCH THE PROBLEM

KNOWNS UNKNOWNS

m = = ?

Δvi = Δvf = = ?

ΔtStrong force = ΔtWeak force = = ?





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Student Edition, pp. 238–241 2. SOLVE FOR THE UNKNOWNS

Determine the initial and final momentum.

Apply the impulse-momentum theorem to determine the impulse.

Use the impulse to determine the force needed to stop the skateboarder.

3. EVALUATE THE ANSWER

• Explain why the magnitude of the force is realistic considering

the times.

Summarize a way that angular momentum is important for ice skating.





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TRY IT !Problem

An object spins with an angular momentum of 8.9 kg�m2/s. A torque on the object causes it to slow to a stop in 5.2 s. What was the angular impulse on the object? What was the average torque on it?

1. ANALYZE AND SKETCH THE PROBLEM

KNOWNS UNKNOWNS

Lf = Li = = ?

Δt = = ?

2. SOLVE FOR THE UNKNOWNS

Determine the angular impulse from the change in angular momentum.

Apply the impulse-momentum theorem to determine the impulse.

3. EVALUATE THE ANSWER

• Is the unit of torque correct?

• Is the magnitude of the torque realistic?

GET IT? Explain why going into a tuck position increases a diver's angular velocity.


Use with Example Problem 2

Use this column for

scratch work and

sketches.





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SUMMARIZE

How does the MAINIDEA for this section relate to the chapter’s BIGIDEA?

REVIEW IT !

10. MAINIDEA Which has more momentum, a truck that is parked or a falling raindrop? Explain.

11. Momentum Is the momentum of a car traveling south different from that of the same car when it travels north at the same speed? Draw the momentum vectors to support your answer.

12. Impulse and Momentum When you jump from a height to the ground, you let your legs bend at the knees as your feet hit the floor. Explain why you do this in terms of the physics concepts introduced in this chapter.

13. Impulse and Momentum A 0.174-kg softball is pitched horizontally at 26.0 m/s. The ball moves in the opposite direction at 38.0 m/s after it is hit by the bat.

a. Draw arrows showing the ball’s momentum before and after the bat hits it.

b. What is the change in momentum of the ball?

c. What is the impulse delivered by the bat?

d. If the bat and ball are in contact for 0.80 ms, what is the average force the bat exerts on the ball?






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14. Momentum The speed of a basketball as it is dribbled is the same just before and just after the ball hits the floor. Is the impulse on and the change in momentum of the basketball equal to zero when the basketball hits the floor? If not, in which direction is the change in momentum? Draw the basketball’s momentum vectors before and after it hits the floor.

15. Angular Momentum The ice-skater in Figure 8 spins with his arms outstretched. When he pulls his arms in and raises them above his head, he spins much faster than before. Did a torque act on the ice-skater? What caused his angular velocity to increase?

16. Critical Thinking An archer shoots arrows at a target. Some of the arrows stick in the target, while others bounce off. Assuming that the masses of the arrows and the velocities of the arrows are the same, which arrows produce a bigger impulse on the target?

Hint: Draw a diagram to show the momentum of the arrows before and after hitting the target for the two instances.

Spinning slowly Spinning quickly

Figure 8





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9 momentum and its conservation - poulin's...

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