Quiz 3.6: Friction Force

What is friction?

• Friction is the force that accelerates motion.

• Friction is the force that opposes motion

• Friction is the force that attracts objects together

• Friction is the force that causes objects to float.

Explain static friction.

• The force that accelerates the sliding motion between two surfaces that are in contact.

• The force that resists the initiation of sliding motion between two surfaces that are in contact and at rest relative to each other

• The force that occurs when two surfaces are not in contact.

• The force that remains constant regardless of the surfaces' contact

Explain kinetic friction.

• The force that helps objects move smoothly against each other

• The force that occurs between stationary objects

• The force that increases the speed of objects in motion

• The force that opposes the relative motion between two surfaces in contact when they are sliding against each other

How is static friction calculated? Select all that applies

• F_s = μ_sF_N

• F_s = μmg

• F_s = μ_smg

• F_s = μ_sF_g

How is kinetic friction calculated? Select all that applies

• F_k = μ_kF_g

• F_k = μ_kF_N

• F_k = μmg

• F_k = μ_kmg

A skier is going down a slope at constant speed. The coefficient of friction between the skier and the incline is .61. Find the angle of inclination.

• 60 degrees
• 20 degrees
• 31.6 degrees
• 45 degrees

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NGSS.HS-PS2-1

NGSS.HS-PS2-4

As the angle of the incline increases, what happens to the normal force?

• Normal force decreases
• Normal force increases
• Normal force becomes negative
• Normal force remains constant

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NGSS.HS-PS2-1

Given the FBD, which of the following must be true?

• The frictional force must be accelerating the system to the left.

• The box must be accelerating to the right.

• The box must be moving to the right.

• The FBD is incorrectly drawn. This situation isn't possible

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NGSS.HS-PS2-1

A box with a weight of 100 N is at rest. It is then pulled by a 30 N horizontal force. Does the box move?

• Yes

• No

• Not enough information to say

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NGSS.HS-PS2-1

A block of mass 5.00 kg rests on a horizontal surface where the coefficient of kinetic friction between the two is 0.200. A string attached to the block is pulled horizontally, resulting in a 2.00 m/s² acceleration by the block. Find the tension in the string. Give your answer to 1 decimal place and include the appropriate unit.

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NGSS.HS-PS2-1