Below are four statements about acceleration. Which statement is not correct? A Acceleration always involves changing speed. B Changing direction always involves acceleration. C Changing speed always involves acceleration. D Circular motion always involves acceleration.

A. Acceleration always involves changing speed.

Explanation:

Acceleration is defined as the rate of change of velocity.

Velocity is a vector quantity and is defined as speed in a given direction. Therefore, when any or both of the components of velocity is changing with time, a body is said to be accelerating i.e. acceleration involves a change of speed or change in direction, or a change in both speed and direction.

Considering the statements:

A. Acceleration always involves changing speed is false because acceleration can occur when speed is constant but direction is changing.

B. Changing direction always involves acceleration is true because, a change in direction results in a change in velocity.

C Changing speed always involves acceleration is true because, changing speed results in a change in velocity.

D. Circular motion always involves acceleration is true because in circular motion the direction is always changing, and this results in a change in velocity