Friction
Real life applications
* Walking: if there is no friction between your shoes or feet and the floor,you would be slippering in one place forever
* Breaks : it is used to stop your car/bike when you step on the breaks.
* When cold, you rub your hands together to warm your hands.the heat comes from friction
* Rubbing the mouse pad of laptops
* Friction is very useful in industry. in wheet flour mill running through the conveyor belt due to friction.
IMPORTANT FORMULAE
1. N=W=mg
2. \(
f_{s\,\,\,\,} = \,\mu _s N = \mu _s mg
\)
3. \(
f_{k\,\,\,\,} = \,\mu _k N = \mu _k mg
\)
4. \(
f_{r\,\,\,\,} = \,\mu _r N = \mu _r mg
\)
5. \(
a = - \mu _k g\)
6. \(
s = \frac{{u^2 }}
{{2\mu _k g}}
\)
7. \(
t = \frac{u}
{{\mu _k g}}
\)
8. \(
a = \frac{{F - \mu _k mg}}
{m}
\)
9. \(
a = (\mu _s - \mu _k )g
\)
10. \(
\mu _s F = mg
\)
FRICTION
The property by virtue of which an opposing force is generated between two rough surfaces in contact with each other and which opposes the sliding of one surface over the other is known as friction.
FRICTIONAL FORCE
The force which opposes the sliding or relative motion of two bodies in contact with each other, is called frictional force.
Frictional force some times may be in the direction of motion of the body
EX :1 If you are walk f a car. When the car is accelerated, direction of frictional force on the rear wheels will be in the direction of motion and on the front wheels in the opposite direction of motion
CAUSES OF FRICTION
1. A surface through appears smooth by visual inspection or by touch, but when viewed under a powerful microscope, it consists of a large number of surface irregularities.
2. When two bodies are placed one above the other, these surface irregularities interlock together and oppose any attempt to bring a relative motion between the bodies.
3. When a sufficiently large force is applied, these irregularities will be sheared off and breaking of locked joints takes place and the body starts sliding on the surface.
4. Friction is due also to cohesive or adhesive force among molecules at close proximity.
ADVANTAGES OF FRICTION :
* Friction plays an important role in our daily life. While walking friction between the ground and shoes prevent us from slipping
* Without friction motion cannot be conveyed by belts from motor to machine
* Vehicles will not come to rest even if the brakes are applied when there is no friction between tyres and the road.
* When there is no friction knots cannot be tied.
* Nails and screws do not hold the boards together without friction.
DISADVANTAGES OF FRICTION :
* Friction causes wear and tear of moving parts of the machinery.
* Friction generates heat in machine parts which damages the machinery.