Acceleration and Retardation

Acceleration is the change in velocity of an object over time. It occurs when an object moves faster or changes direction. Force causes acceleration. The rate of change of velocity is called acceleration.

• If the velocity changes by equal amounts in equal time intervals, the object is said to be in uniform acceleration.
• If the velocity changes by unequal amounts in equal time intervals, the object is said to be in non-uniform acceleration.

Formula:

Acceleration = `"Change in velocity" / "Time taken for change"`

If the initial velocity is ‘u’ and in time ‘t’ it changes to the final velocity ‘v’,

Acceleration = a = `"Final velocity – Initial velocity"/"Time"`

a=`"(v-u)"/"t"`

For example,

A truck travels at 60 km/hour on the first part (AB), 30 km/hour on the second part (BC), and 40 km/hour on the third part (CD). The truck's speed changed several times, meaning it experienced acceleration. 

Retardation occurs when an object slows down. It is also known as negative acceleration.

For example,

• When a car slows down while approaching a red light, it experiences retardation.
• A football rolling on the ground eventually stops due to the friction acting on it.

1. Aim: To observe how the velocity of a ball changes as it rolls down an inclined channel.

2. Requirements: A 1-meter-long plastic tube (cut lengthwise into two halves), a small ball (e.g., marble), a flat surface to place the setup, and a ruler (optional for measuring the height).

3. Procedure

• Cut the plastic tube lengthwise into two halves, creating a channel.
• Place one end of the channel on the ground and elevate the other end to form an inclined slope.
• Place the ball at the elevated end of the channel and release it without applying any external force.

Observe the ball as it rolls down:

• At the top of the channel (start point).
• At the middle of the channel.
• At the bottom of the channel (end point).

Change in velocity

4. Observations: The velocity of the ball is not the same at all points. The ball starts slowly at the top, accelerates through the middle, and moves fastest at the bottom.

5. Conclusion: The velocity of the ball increases as it moves down due to gravity. The incline causes the ball to accelerate, making it move faster as it gets closer to the bottom. This experiment demonstrates the effect of gravitational force on objects moving along an inclined surface.