NCERT Solutions for Class 8th Science
Chapter 12. Friction
- Friction opposes the relative motion between two surfaces in contact. It acts on both the surfaces.
- The force of friction always opposes the applied force.
- Spring balance is a device used for measuring the force acting on an object.
- Friction can also produce heat. Vigorously rub your palms together for a few minutes.
- Friction depends on the nature of surfaces in contact.
- The substances which reduce friction are called lubricants.
- When one body rolls over the surface of another body, the resistance to its motion is called the rolling friction.
- When one body slides over the surface of another body, the resistance to its motion is called the sliding friction.
- Static friction comes into play when we try to move an object at rest.
- Rolling friction is smaller than the sliding friction.
- Sliding friction is smaller than static friction.
- The frictional force exerted by fluids is also called drag.
- Friction can be increased by making a surface rough.
- Friction can be reduced by using lubricants.