Force and Pressure: Friction Force

Understanding Friction Force. Factors affecting Friction Force. Application of Friction Force.

Learner's Guide


In this session we will learn:

    1. What is friction?
    2. What are different type of friction force?
    3. On what factors, friction force depends?
    4. Why is friction important?
    5. What are the disadvantages of friction?
    6. What can be done to increase or reduce friction?


What is Friction?


Friction is caused by:

  1. Molecular Force
  2. Roughness of force
  3. Stickiness of surface
  4. All of above.
Show|Hide Answer


roughness of surface.



Types of Friction:




When you ride the bicycle, which friction you face?

  1. Static
  2. Kinetic
  3. Rolling
  4. Sliding
Show|Hide Answer


Kinetic and Rolling.



Advantages and disadvantages of Friction:




Why do you need to constantly pedal the bicycle?

Show|Hide Answer


Kinetic friction acts in opposite direction of cycle movement and slows it down. By constant peddling, we are able to maintain the speed.


How to increase and decrease the friction:




  • Both the objects in image are made of iron.
  • Both the objects have same surface area.
  • Both the objects have same mass.

When dragged or slid on surface, which object will face maximum friction?

Show|Hide Answer


Friction depends on contact area. More the contact area, more will be friction force.

For sphere contact area will always be less and thus it will fave minimum friction force.


Tip: Think before answering.

  • Which of the following is easier to pedal?

    Difficulty Level: Moderate

    A as it has less weight

    Less weight means less friction.

  • Which of the following will lead to increase in friction?

    1. Applying lubricants
    2. Increasing surface area
    3. Reducing surface area
    4. Reducing weight
    Difficulty Level: Easy

    Increasing surface area

  • Friction depends on _______

    1. Roughness
    2. Weight
    3. Surface Area
    4. Contact area
    5. All
    Difficulty Level: Moderate
  • Friction acts in same direction of movement.

    True or False?

    Difficulty Level: Easy


    Friction always act in opposite direction of movement.

  • Friction results in production of heat.

    True or False?

    Difficulty Level: Easy


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