**Uniform Circular Motion**

-A body moving with constant speed on the circle

-Acceleration is Directed towards centre

a=v

^{2}/r

Where v is the speed and r is the radius of the circle

-Centrepetal force is required to move the body in the circle

F=mv

^{2}/r

**Friction:**

Frictional force acts between the bodies whenever there is a relative motion between them.

When bodies do the slip ,frictional force is called static frictional force and when the bodies does not slip ,it is called kinetic frictional force.

**Kinetic Frictional force:**-When bodies slip over each other

f=μ

_{k}N

Where N is the normal contact force between the surface

And μ

_{k}is the coefficent of kinetic Friction

Direction of frictional force is such that relative slipping is opposed by the friction

**Static Frictional force:**

-Frictional force can also act even if there is no relative motion.Such force is called static Frictional force

-Maximum Statix friction that a body can exert on other body in contact with it is called limiting Friction.

f

_{max}=μ

_{s}N

Where

N is the normal contact force between the surface

And μ

_{s}is the coefficent of static Friction

f

_{max}is the maximum possible force of static Friction

Some Imp points

1. μ

_{s}> μ

_{k}

2 Angle of friction tanλ=μ

_{s}

**Frame Of refrence:**

**Inertial Frame Of refrence:**

-Inertial frame of refrences are objects which are at rest or moving at constant Velocity

-Exmaple:A person standing in a train moving at constant velocity

-Newtons law are valid

**Non Inertial Frame Of refrence:**-Inertial frame of refrences are objects which are accelerated

-Exmaple: A person standing in a train moving with increasing speed.

-Newtons law are not valid.

To apply newtons law ,pseudo force has to be introduced in the equation whose value will be

F=-ma

where a is the accelration of the non inertial frame of refrence

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