Question

The distance between two station is 3 km. A locomotive starting from one station gives the train an acceleration (reaching a speed of 40kmph in 0.5minutes) until the speed reaches 48kmph. This speed is maintained until brakes are applied and the train is brought to rest at the second station under retardation of 1m/sec. Find the time taken to perform this journey.​

Answer 1

Answer:

on is

C

54 km/h

We have 60=v=u+at

1

=at

1

⇒a=

t

1

60

Also, s

1

=ut

1

+

2

1

at

1

2

=

2

1

t

1

60

t

1

2

=30t

1

Now, v

2

=u

2

+2as

1

From, s

1

=

2

1

at

1

2

we substitute a=

t

1

2

2s

1

⇒ v=

t

1

2s

1

The s

2

distance is traveled at this velocity. Thus we get:

s

2

=vt

2

=

t

1

2s

1

t

2

But the ratio of times is given as

t

1

t

2

=

1

8

or t

2

=8t

1

⇒ s

2

=16s

1

And we got s

1

=30t

1

⇒ s

2

=480t

1

Given: s

3

=s

1

=30t

1

Thus, we get the average speed as:

time taken

distance travelled

=

t

1

+8t

1

+t

1

30t

1

+480t

1

+30t

1

=54 km/hr