Question

find the initial velocity of a car which is stopped in 5 sec by applying brakes . the retardation due to brake is 1.5m/s ​

Answer 1

Answer:

Initial velocity is 7.5 m/s

Explanation:

Given:

1. Time taken for the complete retardation (t) = 5s

2. Retardation (a)= -1.5m/s^2

3. Final velocity (v)= 0

To find:

1. Intial velocity (u)= ?

Solution:

For a uniformly accelerated or retarded motion in a straight line we have,

v = u + at

or, 0 = u + (-1.5)*5

or, u = 1.5*5

or, u = 7.5m/s

Answer 2

Answer:

The initial velocity is 7.5m/s

Explanation:

we know that initial velocity, u ,final velocity v , acceleration a and time t is related by the second equation of motion

$v - u = at \: \: or \: v = u + at$

According to the given question we have following:

initial velocity = u

final velocity, v = 0 ( car stops because breaks are applied)

acceleration,a = (-1.5)m/s^2 [ because retardation is negative acceleration]

time ,t =5 s

therefore

$0 - u = ( - 1.5) \times 5 \\ \\ u =7 .5m {s}^{ - 1}$

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