Question

A truck is moving with the velovity of 72km/h. When the driver applies brakes,the truck comes to rest in 2 seconds. Calculate the retardation and distance covered by the truck.

Answer 1

Explanation:

v=u+at

0=72+2a

-72=2a

a=36

Answer 2

Answer:

Explanation:

Solution,

Here, we have

Initial velocity, u = 72 km/h = 72 × 5/18 = 20 m/s

Final velocity, v = 0 m/s (As brakes applied)

Time taken, t = 2 seconds

To Find,

Retardation, a = ?

Distance covered, s = ?

We know that

Acceleration formula,

a = v - u/t

⇒ a = 0 - 20/2

⇒ a = - 20/2

⇒ a = - 10 m/s²

Hence, the Retardation of truck is - 10 m/s².

Now, we know that

3rd equation of motion,

v² - u² = 2as

⇒ (0)² - (20)² = 2 × (- 10) × s

⇒ 400 = - 20s

⇒ 400/20 = s

⇒ s = 20 m

Hence, the distance covered by truck is 20 m.