At uniform speed the acceleration is

Acceleration is defined as the rate of change of velocity with respect to time. Velocity is a vector quantity, meaning it includes both speed and direction. In the context of uniform linear motion, an object moves along a straight line at a constant speed [2]. Because the speed is constant and the direction of motion does not change, the velocity remains constant [2]. When velocity is constant, there is no change in velocity over time, which mathematically results in an acceleration of zero [1]. While uniform circular motion involves constant speed with non-zero centripetal acceleration due to changing direction, the standard interpretation of 'uniform speed' in basic kinematics—especially when contrasted with non-uniform linear motion—implies zero acceleration [1]. Therefore, at a uniform speed in a fixed direction, the acceleration is zero.

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 8: Measurement of Time and Motion > 8.4 Uniform and Non-uniform Linear Motion > p. 117
2. [2] Science-Class VII . NCERT(Revised ed 2025) > Chapter 8: Measurement of Time and Motion > In a Nutshell > p. 118