Question

A driver of a car moving at 30 m/s suddenly notices a child 80 m straight ahead. If the driver’s reaction time is 0.5 s and the deceleration is 8 ms-2, can he avoid hitting the child?

Answer 1

Given :

• Initial velocity (u) = 30 m/s
• Distance between boy and car (s) = 80 m
• Time interval (t) = 0.5 s
• Retardation (a) = - 8 m/s²
• Final velocity (v) = 0 m/s

To Find :

• Can he avoid hitting.

Solution :

If distance travelled by car comes to be less than 80 m. he can avoid hitting.

Use 3rs equation of motion :

⇒v² - u² = 2as

⇒0² - (30)² = 2 * - 0.8 * s

⇒- 900 = - 1.6s

⇒s = 900/1.6

⇒s = 526.5

$\therefore$ Distance travelled by car before coming to rest is 526.5 m.

___________

• So, he can avoid hitting