Question

a car travels hundred kilometer distance at a speed of 60 kilometers per hour and returns with a speed of 40 kilometers per hour. Calculate its average speed for the whole journey​

Answer 1

Answer:

Given:

Car travels 100 km distance at speed of 60 km/hr and returns at a speed of 40 km/hr

To find:

Average speed for the entire journey

Concept:

Average speed is defined as the ratio of total distance to the total time taken to travel the total distance.

Since , distance term is involved , average speed is always positive.

Calculation:

$avg. \: v = \dfrac{total \: distance}{total \: time}$

$= > avg. \: v = \dfrac{(100 + 100)}{ \dfrac{100}{60} + \dfrac{100}{40} }$

Cancelling all the necessary terms :

$= > avg. \: v = \dfrac{2}{ \dfrac{1}{60} + \dfrac{1}{40} }$

$= > avg. \: v = \dfrac{2}{ \bigg \{\dfrac{2 + 3}{120} \bigg \}}$

$= > avg. \: v = \dfrac{2 \times 120}{5}$

$= > avg. \: v = 48 \: km \: {hr}^{ - 1}$

So final answer is :

$\boxed{ \red{ \huge{ \bold{avg. \: v = 48 \: km \: {hr}^{ - 1} }}}}$

Answer 2

$\large{\underline{\underline{\mathfrak{Answer :}}}}$

• Average velocity is 48 km/h

$\rule{200}{0.5}$

$\underline{\underline{\mathfrak{Step-By-Step-Explanation :}}}$

Given :

• Velocity of car in 1st case (v1) = 60 km/h
• Velocity of car in 2nd case (v2) = 40 km/h

$\rule{200}{2}$

To Find :

• Average velocity of car

$\rule{200}{2}$

Solution :

We have formula for Average velocity :

$\large{\boxed{\sf{v_{avg} \: = \: \dfrac{2v_1 v_2}{v_1 \: + \: v_2}}}} \\ \\ \implies {\sf{v_{avg} \: = \: \dfrac{2 \: \times \: 40 \: \times \: 60}{40 \: + \: 60}}} \\ \\ \implies {\sf{v_{avg} \: = \: \dfrac{2 \: \times \: 2400}{100}}} \\ \\ \implies {\sf{v_{avg} \: = \: \dfrac{4800}{100}}} \\ \\ \implies {\sf{v_{avg} \: = \: 48}} \\ \\ \underline{\sf{\therefore \: Average \: velocity \: of \: car \: is \: 48 \: kmh^{-1}}}$

$\rule{200}{2}$

$\large{\underline{\underline{\mathfrak{Additional \: Information \: :}}}}$

• Velocity is defined as rate of change of displacement.

• Velocity can be positive or zero.

• SI unit of velocity is m/s.

• It is a vector quantity.

$\rule{200}{2}$

For derivation of the above formula, see here :

https://brainly.in/question/16417933