Question

Question #6e96b

Answer 1

`v = 8sqrt(5)"m/s"`

Explanation:

Just after bus started
For bus: Displacement, `x = (1/2)` x `(0.2)` `t^2`
For man: Displacement, `80 + x = vt`

To get close to the bus:

`0.1 * t^2 = vt - 80` ; eliminating `x` from above two equations

=> `t^2 -10vt +800 = 0`

To get the real solution of the above quadratic equation;

`10v^2 - 4 * 1 * 80 >= 0`

This means that

`v^2 >= 320`

so, the minimum speed will be

`sqrt(v^2) = sqrt(320) => v = 8sqrt(5)"m/s"`