First slide

Rectilinear Motion

Question

A car covers the first half of the distance between two stations at a speed of 30 kmph and the others half at 60 kmph. Then its average speed is

Easy

A

40 kmph
B

50 kmph
C

45 kmph
D

90 kmph

Solution

$A v e r a g e s p e e d = \frac{Total dis tan cecovered}{Total timetaken} = \frac{\frac{S}{2} + \frac{S}{2}}{t_{1} + t_{2}}$
Where S=Total distance
$\begin{array}{l} t_{1} = \frac{S}{2 V_{1}} \\ t_{2} = \frac{S}{2 V_{2}} \end{array}$
$\begin{matrix} ∴ Average Speed = \frac{(\frac{S}{2}) + (\frac{S}{2})}{\frac{S}{2 (V_{1})} + \frac{S}{2 (V_{2})}} \\ = \frac{S}{\frac{S}{2} (\frac{1}{V_{1}} + \frac{1}{V_{2}})} \\ = \frac{2 V_{1} V_{2}}{V_{1} + V_{2}} = \frac{2 \times 30 \times 60}{30 + 60} \\ = \frac{2 \times 1800}{90} \end{matrix}$
$= 40 kmph$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App