Question

find the initial velocity of a car that is stopped in 10s by applying breaks. retardation due to breaks is 2.5ms-^2

Answer 1

ANSWER :

Given :

▪ Stopping time = 10s

▪ Retardation of car = 2.5m/s^2

To Find :

▪ Initial velocity of car.

Formula Derivation :

✏ This question is completely based on concept of stopping (reaction) time.

✒ v = u + at

✒ 0 = u + (-a)t

✒ u = at

✒ t = u/a

• t denotes reaction time
• u denotes initial velocity
• a denotes retardation

Calculation :

→ t = u/a

→ u = at

→ u = 2.5 × 10

→ u = 25m/s

Answer 2

Given:

★ Stopping time (t) = 10 seconds

★ Acceleration (a) = -2.5 m/s²

★ Final Velocity (v) = 0 [As brakes are applied]

To Find :

• Initial Velocity (u)

Some important Formulae :

→ v = u + at

→ s = ut + 1/2at²

→ 2as = v² - u²

Solution:

By using the formula,

v = u + at

0 = u + (- 2.5)×10

0 = u - 2.5×10

0 = u - 25

25 = u

Therefore, initial velocity of the car after applying breaks is 25 m/s .