Question

A body is at $y=8t-3t^2$ from origin along $y-axis$. The average speed during $4s$ from origin is

• A. $4m{s}^{-1}$
• B. $2m{s}^{-1}$
• C. $-2m^{-1}$
• D. $-4m{s}^{-1}$

Answer 1

Answer: (D)

Putting t = 0 we get $y=8t-3t^2=0$ and at t = 4 we get y =$8\times 4-3\times 4^2=-16$
Average velocity = $\frac{-16-0}{4}=-4m{s}^{-1}$