Question

An object is moving in a straight-line path has a velocity of $40\text{m/s}$ at some instant. After $5\text{s}$, its velocity changed to $30\text{m/s}$. What is the average acceleration of the ball during this time interval?

• A. $2{\text{m/s}}^2$
• B. $-2{\text{m/s}}^2$
• C. $-4{\text{m/s}}^2$
• D. $4{\text{m/s}}^2$

Answer 1

The correct option is B $-2{\text{m/s}}^2$

Average acceleration of the object is given by
$\overline{a}=\frac{v_f-v_i}{t}$ where, $v_f$ is the final velocity of the object, $v_i$ is the initial velocity of the object and $t$ is the time taken by object to attain the final velocity from initial.
Hence, average acceleration is given by
$\overline{a}=\frac{30-40}{5}=-2{\text{m/s}}^2$