Friction - AP Physics 1: Unit 2 Review Supplement

Which statement accurately describes the relationship between the coefficient of static friction (μ_s) and the coefficient of kinetic friction (μ_k) for a given pair of surfaces?

• μ_s is always less than μ_k.

• μ_s is always equal to μ_k.

• μ_s is always greater than or equal to μ_k.

• The relationship between μ_s and μ_k varies unpredictably.

For an object resting on a horizontal surface, what is the magnitude of the normal force acting on the object?

• Equal to the object's mass.

• Equal to the object's weight.

• Always greater than the object's weight.

• Always less than the object's weight.

A block of mass m_b on a table is attached to a string that goes over an ideal pulley and is attached to a cube of mass m_c. The block and cube are currently at rest. If the coefficient of static friction between the block and the table is μ_s, what is the magnitude of the force preventing the block from accelerating?

• μ_s * m_b * g

• μ_k * m_b * g

• (m_c + m_b) * g

• m_c * g

A book with mass 'm' is at rest on an incline of angle 'θ'. If the coefficient of static friction between the book and the incline is μs, and the coefficient of kinetic friction is μk, what is the magnitude of the static friction force currently acting on the book?

• μs mg cosθ

• μk mg cosθ

• mg cosθ

• mg sinθ

A stationary object on a surface experiences a static friction force. Which of the following statements about this force is correct?

• The static friction force is always equal to the coefficient of static friction multiplied by the normal force.

• The static friction force is always less than the coefficient of static friction multiplied by the normal force.

• The static friction force is always less than or equal to the coefficient of static friction multiplied by the normal force.

• The static friction force is always greater than the coefficient of static friction multiplied by the normal force.

A 20 kg block is placed on a horizontal table. What is the magnitude of the normal force exerted by the table on the block? (Assume g = 10 m/s²)

• 20 N

• 140 N

• 200 N

• 2000 N

A 20 kg block is at rest on a table. A horizontal force of 140 N is applied to the block, but it is not enough to move it. Which statement accurately describes the coefficient of static friction (μs) between the block and the table? (Assume g = 10 m/s²)

• μs ≥ 0.7

• μs = 0.7

• μs ≤ 0.7

• μs = 1.4