Question

A police van moving on a highway with a speed of 30 km/h fires a bullet at a thief s car speeding away in the same direction with a speed of 192 km/h. If the muzzle speed of the bullet is 150 km/h, with what speed does the bullet hit the thief s car?

• A. 105 m/s
• B. 205 m/s
• C. 210 m/s
• D. 250 m/s

Answer 1

Answer: (A)

Speed of thiefs car w.r.t. ground
$v_T=192km/h$
Speed of police van w.r.t. ground
$v_P=30km/h$
Speed of bullet w.r.t. police van
$v_B=150m/s=540km/h$
Speed with which the bullet will hit the thiefs car will be
$v=v_{BG}+v_{GT}$
$v=v_B+v_P+v_T$
$=540+30-192$
$[\because v_G=-v_T]$
$=378km/h$ $=378\times \frac{1000}{3600}m/s$
$=105m/s$