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Motion II
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Differences between speed and velocity
Speed

Velocity

It is defined as the rate of change of distance

It is defined as rate of change of displacement

Speed=Distance/Time v=s/t

Velocity=Displacement/Time v=?/t

It is a Scalar Quantity

It is a Vector Quantity

Speed of an object can never be zero if in motion

It can be zero ,positive or negative depending on displacement

SI Unit is m/s

SI Unit is m/s


Differences between Average speed and Average velocity.
Average speed

Average velocity

It is defined as the ratio total distance covered to total time taken.

It is defined as the ratio total displacement to total time taken.

SI Unit is m/s

SI Unit is m/s

Equation of motion
Acceleration – It is defined as the rate of change of velocity or change in velocity or change in velocity per unit time.
Acceleration=Final VelocityInitial Velocity/Tim; a=vu/t
Types of Acceleration
Uniform Acceleration When the velocity of an object changes uniformly at regular intervals of time. For example: a freely falling object has uniform acceleration.
NonUniform Acceleration  When the velocity of an object changes uniformly at irregular intervals of time or vice versa or both. For example: a moving vehicle on a busy road.
Zero Acceleration When the velocity of an object does not change and remains constant throughout a given interval of time then the object is said to have zero acceleration.
Retardation/Deceleration/Negative AccelerationWhen the velocity of an object decreases with time for a given interval of time then it is said to retard. The magnitude of acceleration is negative because final velocity is less than the initial velocity. For Example : When an object stops on applying brakes.
Equations of motion
1. v=u+at v=final velocity a=acceleration
2. s= ut+at^{2}/2 u=initial velocity s=distance
3. v^{2}u^{2}=2as t=time taken
NOTE
When an object starts from rest ‘u’ is zero and when it comes to rest ‘v’ is zero.
When an object retards ‘a’ is negative.
Identify the given and choose an equation which has at least 3 known variables.
Graphical Interpretation
Distance/Time graph
Uniform Motion The Distance /Time graph of an object moving in uniform motion is a straight line which passes through the origin. We can obtain speed from the slope of the graph.
Slope = tan? Slope = y_{2}y_{1}/x_{2}x_{1 }Where y is taken from the distance and y_{2}y_{1 }
Where x is taken from the time and x_{2}x_{1 }
RestThe graph of an object at rest is a straight line which is parallel to the x axis.
NonUniform motionThe graph of an object with nonuniform motion is a curve line. The slope cannot be calculated.
