2.7 Kinetic and Static Friction

• The formula for static friction is \( F_{s} \leq \mu_{s} N
• The static friction force can exceed the product of the coefficient of static friction and the normal force.

  False
• The value of kinetic friction is constant once movement begins.


  True
• Match the comparison point with its correct description:

  Static friction ↔️ Surfaces at rest

  Kinetic friction ↔️ Surfaces in motion
• The coefficient of static friction is generally higher than the coefficient of kinetic friction.


  True
• What is the normal force in the context of friction?

  Force perpendicular to surface
• The formula for static friction is \( F_{s} \leq \mu_{s} \)N
• Which friction coefficient is generally higher in magnitude?

  Static friction coefficient
• Static friction opposes relative motion between surfaces that are at rest
• Kinetic friction opposes relative motion between surfaces that are in motion
• Kinetic friction is constant and acts once movement has begun.


  True
• Steps to apply friction formulas in problem-solving:

  1️⃣ Identify forces, including the normal force

  2️⃣ Determine if the object is at rest or in motion

  3️⃣ Select the appropriate friction formula

  4️⃣ Calculate the friction force
• What is static friction?

  Force opposing motion at rest
• What does \(\mu_{s}\) represent in the static friction formula?

  Coefficient of static friction
• Match the type of friction with its formula:

  Static friction ↔️ \( F_{s} \leq \mu_{s} N \)

  Kinetic friction ↔️ \( F_{k} = \mu_{k} N \)
• What is kinetic friction?

  Force opposing motion in motion
• The formula for kinetic friction is \( F_{k} = \mu_{k} N
• What does \(\mu_{k}\) represent in the kinetic friction formula?

  Coefficient of kinetic friction
• What happens to kinetic friction once movement starts?

  It remains constant
• The kinetic friction force is equal to the product of the coefficient of kinetic friction and the normal force.

  True
• Match the type of friction with its context:

  Static Friction ↔️ Surfaces at rest

  Kinetic Friction ↔️ Surfaces in motion
• Stronger surface bonds require more energy to initiate movement in static friction.


  True
• What does \( \mu_{s} \) represent in the static friction formula?

  Coefficient of static friction
• The static friction force can be equal to or less than \( \mu_{s} N \) up to a maximum value.


  True
• What is the formula for kinetic friction?

  $F_{k} =$$\mu_{k} N$
• What happens to the static friction force if an applied force is less than its maximum value?

  It balances the applied force