5 displacement and force in two...

MAINIDEAWrite the Main Idea for this section.

Recall and write the definition of the Review Vocabulary term.

force

Use your book to answer the questions below.

1. Compare and contrast kinetic friction and static friction.

2. The slope of a line on a kinetic friction force v. normal force graph

is called the coefficient of

kinetic friction and relates the friction force to normal force.

3. In the equation for the maximum static force, μs is the

between two surfaces.

REVIEW VOCABULARY

force

4(B), 4(D), 4(E)

5 Displacement and Force in Two Dimensions 2 Friction

NEW VOCABULARY kinetic friction

static friction

coefficient of kinetic

friction

coefficient of static

friction

Science Notebook • Displacement and Force in Two Dimensions78

Program: TX HS Science Component: PPP SCI NTBKPDF PASS

Vendor: LASERWORDS Grade: N/A

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ission is granted to reproduce for classroom use.

Describe the influence of static and kinetic friction when you are pushing a couch.

GET IT? Identify the two factors that affect friction forces.

Write the equation for the kinetic friction force in the box, and state the equation in words on the lines below.

Write the equation for the static friction force in the box, and state the equation in words on the lines below.

Student Edition, pp. 130–132

2 Friction (continued)





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Describe how coefficients of friction are measured, and identify factors that can affect those measurements.

Complete the table below using your textbook.

Typical Coefficients of Friction*

Surfaces Coefficient of static friction (μs)

Coefficient of kinetic friction (μk)

Glass on glass

Oak on oak

Steel on steel

*All measurements are for dry surfaces unless otherwise stated.

TRY IT !

ProblemBALANCED FRICTION FORCES You push a 35.5-kg wooden box across a wooden floor at a constant speed of 1.5 m/s. The coefficient of kinetic friction is 0.15. How large is the force that you exert on a box?

1. ANALYZE AND SKETCH THE PROBLEM

KNOWNS

m = v =

a = μk =

UNKNOWN

= ?

Student Edition, pp. 132–133

Use with Example Problem 3.

Use this column for

scratch work and

sketches.






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Student Edition, p. 133 TRY IT ! (CONTINUED)

2. SOLVE FOR THE UNKNOWN

The normal force is in the y-direction, and the box does not accelerate in that direction.

The pushing force is in the x-direction; v is constant, thus the box does not accelerate.

3. EVALUATE THE ANSWER

• Does the answer make sense?


SUMMARIZE

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

REVIEW IT !

27. MAINIDEA Compare static friction and kinetic friction. How are the frictional forces similar, and how do the forces differ?





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28. Friction At a wedding reception, you notice a boy who looks like his mass is about 25 kg running across the dance floor then sliding on his knees until he stops. If the coefficient of kinetic friction between the boy’s pants and the floor is 0.15, what is the friction force acting on him as he slides?

29. Velocity Dinah is playing cards with her friends, and it is her turn to deal. A card has a mass of 2.3 g, and it slides 0.35 m along the table before it stops. If the coefficient of kinetic friction between the card and the table is 0.24, what was the initial speed of the card as it left Dinah’s hand?

30. Force The coefficient of static friction between a 40.0-kg picnic table and the ground below that table is 0.43. How large is the greatest horizontal force that could be exerted on the table without moving the table?

31. Acceleration You push a 13-kg table in the cafeteria with a horizontal force of 20 N, but the table does not move. You then push the table with a horizontal force of 25 N, and it accelerates at 0.26 m/s2. What, if anything, can you conclude about the coefficients of static and kinetic friction?

32. Critical Thinking Rachel is moving to a new apartment and puts a dresser in the back of her pickup truck. When the truck accelerates forward, what force accelerates the dresser? Under what circumstances could the dresser slide? In which direction?





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5 displacement and force in two...

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