Question

7. A car is travelling along a road at 30 ms when a pedestrian steps into the road 55 m ahead. The

driver of the car applies the brakes after a reaction time of 0.5 s and the car slows down at a rate of
10 ms. What happens?

Answer 1

Answer: Car collide with man

Step-by-step explanation:

Given

Speed of car is
`u=30\ m/s`

Distance of the man from the car is
`s=55\ m`

Reaction time
`t_r=0.5\ s`

Rate of deceleration
`a_d=-10\ m/s^2`

Distance traveled in the reaction time
`d_o=30* 0.5=15\ m`

Net effective distance to cover
`d=55-15=40\ m`

Distance required to stop the car

`\Rightarrow v^2-30^2=2(-10)(s)\\\Rightarrow 0-900=-20s\\\Rightarrow s=45\ m`

Require distance is more than that of net effective distance. Hence, car collides with the man.