Sandhya
- 1. FRICTON
- 2. PRESENTED BY SANDHYA V S PHYSICALSCIENCE
- 3. Suppose you decide to ride a skate board You push off the ground and start moving According to Newtons second law of motion ,if no other forces are acting on your skateboard , you will continue to move.BUT
- 4. The reason is that there exist a force between the ground and lower portion of the skateboard, called FRICTIONAL FORCE.
- 5. Friction is the force which opposes relative motion between two surfaces in contact with each other
- 6. Even though a surface may look smooth, if you magnify the surface it isnt smooth. Everything is made of molecules. The molecules come together to make bumps. Some surfaces have molecules that leaves large bumps and some leaves small bumps. Micro welds occur when two bumpy surfaces are rubbed up against each other they stick together.
- 7. Static friction Frictional force between two surfaces before there is a relative force between the surfaces in contact. Kinetic friction It is the force of friction which calls in to play when there is relative force between the surfaces.
- 8. Rolling friction Rolling friction between two surfaces in contact is the force of friction which calls into play when a body rolls over another. Sliding friction sliding friction is the force that opposes the motion of two surfaces sliding past each other.
- 9. Helps us in walking conveniently. It save us from slipping. Helps us in writing on piece of paper. Helpful in eating and drinking Lighting a match stick by rubbing. Nails and screws join two surfaces due to the friction. we can not climb a tree. Trains can run on the rails. In fact life become impossible if there is no friction in nature.
- 10. Due to friction the whole energy given to a machine is not converted in to useful work; a portion of energy is wasted to overcome friction.This reduces the efficiency of the machine. The energy used in overcoming friction appears as heat. Moreover, friction causes wear and tear of the moving parts of the machine due to rubbing.
- 11. Thus FRICTION IS A NECESSARY EVIL
- 12. It is not possible to walk or drive through muddy and slippery roads. For this sand and gravels are spread to reduce friction Tyres of our vehicles also the soles of the shoes are grooved. Mountaineers also wear spiked shoe. To overcome skidding along a slippery surface we adopt measures to increase friction.
- 13. Reduce the area of contact of two surfaces. Making the surfaces as smooth. Lubrication can reduce friction. Using ball bearings.
- 14. THANK YOU