Question

A car travels from A to B at a speed of 40 km h-1
and returns back on the same track at a speed of
60 km h-4. Average velocity will be
with solution ​

Answer 1

Let distance from A to B = x km

Distance from B to A = x km

• Same distance as A to B

Speed of the car from A to B = 40 km/h

Speed of the car from B to A = 60 km/h

Average Velocity : It is defined as total displacement per total time

$\pink{\bigstar}\ \; \sf V_{Avg}=\dfrac{Total\ displacement}{Total\ time}$

Here the car comes to initial position i.e., to A after moving from A to B . So , displacement of the car is zero .

Note : Displacement of a body for closed path is zero

$\to \sf V_{Avg}=\dfrac{0}{t}\\\\\to \sf \green{V_{Avg}=0\ m/s}\ \; \bigstar$

More Info :

$\to \sf V_{Avg}=\dfrac{0}{t_{A\to B}+t_{B\to A}}$

• Time = Distance / Speed

$\to \sf V_{Avg}=\dfrac{0}{\frac{x}{40}+\frac{x}{60}}\\\\\to \sf V_{Avg}=\dfrac{0}{x\bigg(\frac{1}{40}+\frac{1}{60}\bigg)}\\\\\to \sf V_{Avg}=\dfrac{0}{\frac{3+2}{120}}\\\\\to \sf V_{Avg}=\dfrac{0}{5}\\\\\leadsto \sf \orange{V_{Avg}=0\ km/h}\ \; \bigstar$