Question

A point moves in a straight line during time $t=0$ to $t=3$according to the law $s=15t–2t^2$. The average velocity is

• A. $3$
• B. $9$
• C. $15$
• D. $27$

Answer 1

The correct option is B

$9$

Step 1: Given data

Motion of a particle, $s=15t–2t^2$

Step 2: Find the average velocity

Velocity $=ds/dt$

$=15–4t$

Velocity at $t=0s$, $v_1=15m/s$

Velocity at $t=3s$, $v_2=3m/s$

Average velocity, $v=\left(v_1+v_2\right)/2$

$$\begin{gathered} =\frac{15+3}{2} \\ =18/2 \\ =9m/s \end{gathered}$$

Hence, option (B) is correct.