Question

A car moves on a straight road for first half time with the constant speed of $20 {m} / {sec}$. and the next half time with a constant speed of 60 ${m} / {sec}$, then calculate average speed.

Answer 1

SOLUTION : $40 {m} / {sec}$.

Total distance $={L}$ and

Total time taken $=t$

A $\frac{x \quad C \quad(L-x)}{t_1=t / 2 \quad t_2=t / 2} B$

Let $x$ and $({L}-x)$ be the distance travelled in time $t_1$ and $t_2$, then

$\qquad x=20 t_1=20 t / 2=10 t$

$\text { And }(L-x)=60 t_2=60 t / 2=30 t$

$\text { Average speed }=\frac{\text { Total distance }}{\text { Total time }}=\frac{10 t+30 t}{t}=40 {m} / {sec} \text {. }$