Speed

Rate of motion can be defined in the form of speed. Speed is distance travelled per unit time. SI unit of speed is m/s. In other units this rate of motion can be measured in cm / s and km / h. Speed is denoted by the symbol v. speed is scalar quantity having only magnitude.

• Uniform speed: If speed is constant with respect to time, then object is moving with uniform speed. For example, if car is moving with 2 km in every 10 sec then car is moving in uniform speed.
• Non uniform speed: If object is moving with changing speed then it is in non uniform motion. In such case, rate of motion is given in form of average speed. Average speed of object is defined as, “total distance travelled by object divided by total time taken”

Average speed(v)= Total distance travelled (s) / Total time taken (t)

Velocity

This rate of motion is defined as speed of object in a specific direction. SI unit of velocity is same as that of speed i.e. m/s. It is denoted by v. velocity is vector quantity having magnitude as well as direction.

• Uniform speed: If direction and speed of an object is constant with respect to time, then velocity is said to be uniform.
• Non uniform speed: If direction or speed or both are changing with respect to time, then rate of motion is non uniform. Hence, rate of motion is calculated in terms of average velocity. Average velocity is arithmetic mean of initial and final velocity.

Average velocity = (Initial velocity + Final velocity) /2
v_av = (u+v)/2

Acceleration

Acceleration is rate of motion in which velocity of object changes with respect to time. It is denoted by a and SI unit is m/s2. Consider, if u is initial velocity and v is final velocity, then acceleration a is

a = (v-u)/t

Acceleration can be positive or negative. If acceleration is in direction of velocity of body then it is said to be positive acceleration. If acceleration is opposite to direction of velocity then it is negative

• Uniform acceleration: If velocity of object is continuously increasing or decreasing, then rate of motion of body is uniform i.e. acceleration is uniform. For example, stone falling from height experiences increase in velocity in equal time interval. Hence, stone is in uniform acceleration
• Non uniform acceleration: If velocity of object is shows random increase and decrease, then rate of motion of body is non uniform. For example, car on road moves with changing velocity in equal time interval, hence, car experiences non uniform acceleration.

Keywords: Speed, Velocity, Acceleration, Uniform speed, nonuniform speed, Uniform velocity, Non uniform velocity, Uniform acceleration, Non uniform acceleration.

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