Question

Which statement correctly describes the differences between positive and negative acceleration? Positive acceleration describes a change in speed; negative acceleration describes no change in speed. Positive acceleration describes no change in speed; negative acceleration describes a change in speed. Positive acceleration describes an increase in speed; negative acceleration describes a decrease in speed. Positive acceleration describes a decrease in speed; negative acceleration describes an increase in speed.

Answer 1

Answer:

Positive acceleration describes an increase in speed; negative acceleration describes a decrease in speed.

Explanation:

Acceleration is defined as:

$a=\frac{v-u}{\Delta t}$

where

v is the final velocity

u is the initial velocity

$\Delta t$ is the time taken for the change in velocity to occur

The value of $\Delta t$ is always positive, so the sign of the acceleration depends on the numerator. More specifically, we have two situations:

- if $v > u$, then it means that the final velocity is greater than the initial velocity, so the acceleration is positive and the speed is increasing

- if $v < u$, then it means that the final velocity is smaller than the initial velocity, so the acceleration is negative and the speed is decreasing

Answer 2

The correct answer is - Positive acceleration describes an increase in speed; negative acceleration describes a decrease in speed.