Test: Friction - 2

In moving part of machine, ball bearing is used to reduce friction because rolling friction is always less than sliding friction or static friction.

The thermos flask keeps hot liquid hot and cold liquid cold by preventing heat loss. Thermos flask have double layered wall in which air is evacuated to prevent heat loss.

The frictional force exerted by fluids is also called as drag. This kinds of frictional force can be reduced by changing the shape of the moving body.

When a matchstick is rubbed on match box fire is produced due to friction. Matchstick contain phosphorous that catch fire easily at very low temperature.

The substances which reduce friction are called lubricants. Lubricants include graphite, oils and greases. Lubricant stick with moving part to reduce friction.

The tyres of car, bus and truck has threads to provide better grips with ground. Threads create more friction with road that helps in better grips on road while moving.

It is easier to hold an earthen pot than steel pot as earthen pot has rough surface than steel that provide more friction and better grips while holding.

Carpenters while fixing screws, grease the tips of screen to decrease the friction. Grease present on screw reduce the friction offered by wood articles.

Friction is a contact force because in friction both the bodies are in direct contact with each other moving in opposite direction.

The shape of fish is streamlined that help in decreasing fluid friction. The narrower part of streamlined shape offer less resistance due to friction.

Friction is called as necessary evils because friction is necessary for even walking. Without friction movement of vehicle is not possible on road.

Friction presents in ground slowdown the speed of rolling body. A body will remain in state of motion on rolling on ground if friction is absent.

Soapy water on floor would make it difficult to walk on floor due to less friction. The irregularities present on floor are reduced by soapy water that reduces the friction drastically.

Fluids also offer resistance while a body is moving in fluid. Streamlined shape is useful for movement in fluid as it offer less resistance due to friction.

Wet marble will offer least friction to run a toy car as the roughness or irregularities in wet marble is reduced due to presence of water.

Friction always works opposite to direction of motion. A moving ball slows down due to frictional force working opposite to direction of motion.

Friction is known as friends as well as enemy because friction is useful as well as harmful for us. Without friction it is impossible to walk on ground or move vehicle. On the other hand friction causes wear and tear in shoes and tyres.

Brakes of vehicle is stopped by using brake fitted in wheels of vehicle. Brakes work on property of friction. Brakes attach with wheel on applying brake that slows down the vehicle.

Friction is caused by irregularities on the two surfaces in contact. These irregularities create locks between the surface that cause friction.