Question

The position of an object moving along x-axis is given by $x=a+b{t}^2$ where $a=8.5m$ b = 2.5 m $s^2$ and t is measured in seconds. Which of the following is true?

• A. Velocity at t =2 sec is zero
• B. average velocity between t = 2, t =4 sec is 15 m/s
• C. velocity at t = 4 sec is 10 m/s
• D. all the above are true

Answer 1

The correct option is B average velocity between t = 2, t =4 sec is 15 m/s

$\begin{array}{c}x=8.5+2.5t^2\\ v=5t\\ att=2\\ x=8.5+2.5\times 4\\ =18.5\\ att=4\\ x=8.5+2.5\times 4\times 4\\ =48.5\\ \therefore \Delta x=30\\ t=2\\ \therefore V_{av}==15m/s\end{array}$

$\therefore$ Option $B$ is correct.