Zero Acceleration Conditions Explained

Acceleration is defined as the rate at which an object's velocity changes. Velocity is a vector quantity, including both speed and direction. Zero acceleration ($a = 0$) occurs only when the velocity ($v$) remains constant.

Constant velocity implies that neither the speed nor the direction of motion changes.

Analyzing Motion Scenarios for Zero Acceleration

We examine each option to see if the velocity is constant:

• Train speeding up: Speed increases, so velocity changes. Acceleration is non-zero.
• Aeroplane taking off: Speed increases significantly, so velocity changes. Acceleration is non-zero.
• Car moving with constant speed on a straight road: Speed is constant, and the direction is constant (straight). Velocity is constant. Therefore, acceleration is zero.
• Ball thrown upward: Velocity changes constantly due to gravity (speed decreases upwards, increases downwards). Acceleration is non-zero (due to gravity).

Conclusion on Zero Acceleration

The only situation exhibiting constant velocity, and hence zero acceleration, is the car moving with constant speed on a straight road.