Question

Categorize the following motion as being either an example of positive(+ve) or negative(-ve) acceleration.
i. Speeding up the motion = ___
ii. Slowing down the motion = ___

• A. $+ve,+ve$
• B. $-ve,+ve$
• C. $-ve,-ve$
• D. $+ve,-ve$

Answer 1

The correct option is D

$+ve,-ve$

We know that,
$a=\frac{v_f-v_i}{t}$, where, $v_f$ is the final velocity and $v_i$ is the initial velocity.
For speeding up, magnitude wise $v_f>v_i$ and for slowing down, $v_i>v_f$ .
So, when an object is speeding up it means the accelaration is in the direction of motion hence acceleration is positive. If an object is slowing down, then its acceleration is in the opposite direction of its motion, its final velocity will be less than its initial velocity and hence the acceleration will be negative.