Question

A bike travelling with an initial velocity ‘u’ uniformly decelerates to a velocity of 40 km/h in 20 seconds. The rate of deceleration is 2.5 m/s^2
. What would be the value of ‘u’? ​

Answer 1

Answer:

use v=u-at put the value of v=40 km/h to change it in v=40*(1000/60*60) meter/sec

u=?

t-20 sec

a-2.5m/sec*sec

Answer 2

The value of initial velocity(u) is 61.1 m/s.

Given:

Initial velocity = u

Final velocity = 40 km/h

Deceleration, a = -2.5 m/s²

Time = 20 seconds

To Find:

The value of initial velocity(u).

Solution:

We are required to find the value of initial velocity(u).

We are given with

a = -2.5 m/s²

v = 40 km/hr

v = 40×(5/18)

v = 200/18

v = 11.1 m/s

t = 20 seconds

From newton's equation of motion

v = u+at ------(1)

On substituting the values of v, a, and t in equation(1) we get

11.1 = u +(-2.5×20)

11.1 = u - 50

u = 50+11.1

u = 61.1 m/s

Therefore, The value of initial velocity(u) is 61.1 m/s.

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