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Q: Which of the following is not true about friction force?
  • A. Friction is the force which opposes motion relative to two surfaces in contact.
  • B. The force of friction that acts when a body is moving (sliding) on a surface is called sliding friction.
  • C. Friction in machines wastes energy and also causes wear and tear.
  • D. Rolling friction is much more than sliding friction, the use of ball bearings in a machine considerably reduces friction.
Correct Answer: Option D - Sliding friction is friction that acts on objects when they are sliding over a surface. Sliding friction is weaker than static friction. While in case of rolling friction it is the friction that acts on objects when they are rolling over a surface. Rolling friction is much weaker than sliding friction or static friction. In case of ball bearings are another use of rolling friction. The out let parts of a wheel or other machine roll rather than slide over on another. The ball bearings, in this wheel reduce friction between the inner and outer cylinders when they turn. It found that. Rolling friction < Sliding friction < Static friction
D. Sliding friction is friction that acts on objects when they are sliding over a surface. Sliding friction is weaker than static friction. While in case of rolling friction it is the friction that acts on objects when they are rolling over a surface. Rolling friction is much weaker than sliding friction or static friction. In case of ball bearings are another use of rolling friction. The out let parts of a wheel or other machine roll rather than slide over on another. The ball bearings, in this wheel reduce friction between the inner and outer cylinders when they turn. It found that. Rolling friction < Sliding friction < Static friction

Explanations:

Sliding friction is friction that acts on objects when they are sliding over a surface. Sliding friction is weaker than static friction. While in case of rolling friction it is the friction that acts on objects when they are rolling over a surface. Rolling friction is much weaker than sliding friction or static friction. In case of ball bearings are another use of rolling friction. The out let parts of a wheel or other machine roll rather than slide over on another. The ball bearings, in this wheel reduce friction between the inner and outer cylinders when they turn. It found that. Rolling friction < Sliding friction < Static friction