Question

On a 140 km track train travels the first 40 km at a uniform speed of 40km/hr.
how fast the train travel the next 90 km so as to average 70 km/hr. for entire
trip
​

Answer 1

In order to understand let us draw a simple representation using give data.

From the above representation

From the above representation,

The total distance travelled by the train, d = 140km

The average velocity of the entire trip,Vav-70km/h

Initial distance travelled, d1-40 km

Velocity at which it travelled the initial 40 km, v1 =40km/h

Remaining distance travelled, d2 = 90km

What we have to find is

• t = total time taken

• t1= time taken to travel the first 40km

• t2= time taken to travel the next 90 km

• v2= the velocity at which the train covered the remaining 70 km.

Let us start our calculation.

In order to calculate the velocity at the second interval of time we need to first find the total time taken by the train to finish the journey.

We know the equation to find the average velocity. i.e.

$\sf \boxed{ \sf \: Average \: velocity = \frac{Total \: distance \: travelled }{Total \: time \: taken \: \: \: }} \\ or \\ \boxed{ V_{av \: } = \frac{d}{t} } \: \: \: - - - (1)$

Using eq (1) we can calculate the value of t i.e

$\: \: \: \: \: \: \: \sf \: t = \frac{d }{ V_{av} }$

$\: \: \: \: \sf \: t = \frac{140km}{70km/h}$

$\sf \: \implies \: t = \frac{ \cancel{140}}{ \cancel{70}}$

$\sf \: \: \implies \: t = 2 \: houre \:$

Similarly,

$\bf \: t_{1} = \frac{ d_{1}}{v_{1}}$

$\bf \: t_{1} = \frac{40km}{40km/h} \\ \\ \bf t_{1} = \frac{\cancel{40}}{\cancel{40}}$

$\bf \implies \: t_{1} = 1 \: hour$

$\sf \: Then \: t_{2} = t - t_{1} \: \: \: - - - - (2)$

$\sf \: By \: substituting \: the \: values of \: t \: and \: t \: in \: equation (2), we \\ \sf \: get \: the \: value \: of \: t_{2} \: as$

$\sf t_{2}=t - t_{1} \\ \sf \: t_{2} = 2 - 1 \\ \sf \: t_{2} = 1 \: hour$

Now we can find the velocity at which the train travelled the remaining 90 km is

$\sf v_{2} = \frac{d_{2}}{t_{2}} \: \: \: \: \: - - - - (3)$

$\sf \: \: v_{2} = \frac{90km}{1 \: hour}$

$\sf \: v_{2 }\: = 90km/h$

With a velocity of 90 km/h the train covered the remaining 90 km in one hour.

Answer 2

Answer:

In order to understand let us draw a simple representation using give data.

From the above representation

From the above representation,

The total distance travelled by the train, d = 140km

The average velocity of the entire trip,Vav-70km/h

Initial distance travelled, d1-40 km

Velocity at which it travelled the initial 40 km, v1 =40km/h

Remaining distance travelled, d2 = 90km

What we have to find is

t = total time taken

t1= time taken to travel the first 40km

t2= time taken to travel the next 90 km

v2= the velocity at which the train covered the remaining 70 km.

Let us start our calculation.

In order to calculate the velocity at the second interval of time we need to first find the total time taken by the train to finish the journey.

We know the equation to find the average velocity. i.e.

Explanation:

With a velocity of 90 km/h the train covered the remaining 90 km in one hour.

Plz mark as brainliest..