Question

1) A train moving at a speed of 18 km/h
comes to rest in 2 min by applying brakes.
What is acceleration ?​

Answer 1

It's is given that the

Initial velocity of train(u)= 18km/h

Time taken by car to come in rest = 2 min =2×60

t =120 seconds

Final velocity of car becomes (v) 0 [ because break applied ]

To find :-

We have to find the acceleration ( deceleration) produced by car

• By using first equation of motion we can find the acceleration produced by car

$\boxed{\sf { v= u+at}}$

Convert initial velocity of car into m/s

$\sf u= \cancel{18}\times \dfrac{5}{\cancel{18}} = 5m/s$

or we know that 1km= 1000m

and 1 hours = 3600seconds

then convert

18×1000/3600 = 5m/s

• t= 120 seconds

$\longrightarrow\sf 0= 5+120\times a\\ \\ \longrightarrow\sf 0-5= 120a\\ \\ \longrightarrow\sf \cancel{\dfrac{-5}{120}}= a\\ \\ \longrightarrow\sf \dfrac{-1}{24}= a\\ \\ \longrightarrow\sf \ \ or \ \ a = -0.04m/s^2$

$\boxed{\sf{\dag\ Acceleration \ [deceleration] \ produced \ by \ car = (-0.04)m/s^2}}$

Formula related to this :-

$\sf \dag\ \ \ s= ut+\dfrac{1}{2}at^2\\ \\ \sf \dag\ \ v^2=u^2+2as$

Answer 2

Answer:

Given –

• Speed of the train = 18 km/hr.
• Comes to rest.
• Time = 2 min = 120 seconds.

To Find –

• Acceleration.

Solution –

Speed in m/s :

➸ 18 * 5/18

➸ 5 m/s is the speed of the train.

Acceleration is said to be the rate of change in velocity or speed.

Hence, Acceleration = (V2 - V1)/t

V2 = 0 m/s (comes at rest)

V1 = 5 m/s

t = 120 seconds

Hence, Acceleration = (0 - 5)/120

➸ Acceleration = -5/120

➸ Acceleration = -1/24

➸ Acceleration = - 0.0416 m/s²

As, the acceleration is negative, we must call it as deceleration.

RELATED TERMS :–

• Distance is said to be the total length of the path travelled.
• Distance is a scalar quantity.
• Displacement is called the shortest distance between the initial and the final position of the body.
• It is a vector quantity.
• A quantity is said to be as scalar when it has magnitude.
• A quantity is said as vector when it has magnitude as well as some direction.
• Speed is called the rate of change of distance.
• It is a scalar quantity.
• Velocity is said to be the rate of change of displacement.
• It is a vector quantity.