Every object in the universe is either at rest or in motion with respect to another object. An object in motion can be measured in terms of displacement over time.

Motion is governed by **Newton’s three laws**.

**Law of Inerti**a: a body is at rest or in uniform motion unless acted upon by an external force.
**Law of linear momentum**: When force acts on a moving object, acceleration is produced. The same amount of force produces greater acceleration in lighter bodies than in heavier bodies. Force = mass x acceleration (f=ma). For free falling objects, it is the acceleration due to gravity (f=mg).
**Law of action and reaction**: For every action, there is an equal and opposite reaction.

Three kinds of motion:

Translational – object moves in the same direction in a straight line

Rotational – object turns about a stationary point

Oscillatory – a form of rotational motion

**Kinematic Equations **(translational motion)

s = distance (displacement)

u = initial velocity

v = final velocity

t = time

a = acceleration

$v=u+at$

$v^2-u^2=2as$

$s=ut+\frac{1}{2}at^{2}$

$s=\frac{u+v}{2}t$

**Units**

Units in MKS:

Distance s is in meters

Time is t in seconds

Velocity is v $\frac{m}{s}$

Acceleration a in $\frac{m}{s^{2}}$

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