Question

m/s2
m/s
(4) 1.5 m/s2
25. A person driving a car with a speed 72 km/h, suddenly sees a boy crossing the road. If the distance moved
. by car, before the person applies brakes is 5 m, the reaction time of the person is
(2) 0.10 s
(4) 0.25 S
(1) 0.5 s
(3) 10 s
RELATIVE VELOCITY
VAL​

Answer 1

Explanation:

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Answer 2

Given :-

Speed of the car = 72 km/h

Distance moved by the car before applying break = 5 m

To Find :-

The reaction time of the person.

Analysis :-

Here we are given with distance and speed of the car.

Substitute the given values such that time equals distance divided by speed, then you can find the time easily.

Solution :-

We know that,

• d = Distance
• t = Time
• s = Speed

Using the formula,

$\underline{\boxed{\sf Time \ taken=\dfrac{Total \ distance}{Total \ speed} }}$

Given that,

Distance (d) = 5 m

Speed (s) = 72 km/h

= 72×5/18 = 360/8 = 20 m/s

Substituting their values,

⇒ t = 5/20

⇒ t = 0.25 sec

Therefore, the reaction time of the person is 0.25 sec.