5.2.3 Work Done & Friction

• What is the definition of work done?


  Work done is the energy transferred when a force causes an object to move in the direction of the force.
• What is the formula for calculating work done?

  Work Done (W) = Force (F) × Distance (d) × cos(θ)
• What does the variable F represent in the work done formula?

  F represents the magnitude of the applied force in Newtons (N).
• What does the variable d represent in the work done formula?


  d represents the distance moved by the object in the direction of the force in meters (m).
• What does θ represent in the work done formula?

  θ represents the angle between the force and the direction of motion.
• What is the value of cos(θ) when the force is in the same direction as the motion?

  cos(θ) = 1.
• In what unit is work done measured?

  Work done is measured in Joules (J).
• How much work is done when a force of 1 Newton moves an object 1 meter in the direction of the force?

  1 Joule of work is done.
• What is the definition of friction?

  Friction is a force that opposes the relative motion between two surfaces in contact.
• What are the two types of friction?

  Static friction and kinetic (or dynamic) friction.
• What is static friction?


  Static friction is the force that resists the start of sliding motion between two surfaces.
• What is kinetic (or dynamic) friction?

  Kinetic friction is the force that opposes the motion of surfaces sliding past each other.
• What factors affect friction?

  Normal force, surface roughness, and type of material.
• How does normal force affect friction?

  More normal force results in more friction.
• How does surface roughness affect friction?

  Rougher surfaces increase friction, while smoother surfaces reduce it.
• How does the type of material affect friction?

  Different materials have different coefficients of friction.
• What happens when work is done against friction?

  Energy is transferred into overcoming the frictional force, often resulting in heat.
• What is the formula for work done against friction?

  Work Done = Frictional Force × Distance.
• In the example of sliding a box, what is the constant frictional force applied?

  The constant frictional force is 100 N.
• Over what distance is the box slid in the example?

  The box is slid over a distance of 5 meters.
• How much work is done against friction when sliding the box?

  500 Joules of work is done against friction.
• What happens to mechanical energy when work is done against friction?

  Mechanical energy is converted into thermal energy.
• What is a real-world application of friction in vehicles?

  Frictional forces are used to slow down or stop vehicles.
• How do brakes in vehicles utilize friction?

  The work done by the brakes against the wheels' motion converts kinetic energy into heat.
• How does lubrication affect friction?

  Lubrication reduces friction between moving parts to decrease the work done to overcome friction.
• What are the steps to calculate the work done against friction in a real-world problem?

  1. Determine the Frictional Force.

  2. Measure or Obtain the Distance.

  3. Apply the Work Done Formula: Work Done = Frictional Force × Distance.
• What are the key concepts related to work done and friction?

  • Work Done: Energy transferred by a force moving an object over a distance, measured in Joules.
  • Friction: A force opposing motion, dependent on normal force and surface properties.
  • Work Done Against Friction: Energy required to overcome friction, often converted to heat.