Question

A bus is moving on a straight road towards north with a uniform speed of 50 km/hour then it turns left through 90$^{\circ}$. If the speed remains unchanged after turning, the increase in the velocity of bus in the turning process is

• A. 70.7 km/hr along south-west direction
• B. zero
• C. 50 km/hr along west
• D. 70.7 km/hr along north-west direction

Answer 1

Answer: (A)

70.7 km/hr along south-west direction

Answer 2

$v_1$ 50 km/hr due north
$v_2$ 50 km/hr due west
- $v_1$ 50 km/hr due south
Magnitude of change in velocity
= $| \overrightarrow{v_2} - \overrightarrow{v_1} | = | \overrightarrow{v_2} + ( - \overrightarrow{v_1}) |$
= $\sqrt{ v_2^2 + ( - v_1)^2 }$
= $\sqrt{ ( 50)^2 + (50)^2 }$
= 70.7 km/hr along south-west direction