Question

A police jeep is chasing with the velocity of $45km/h$, to a thief car moving with velocity $153km/h$ on a straight road. Police fires a bullet with muzzle velocity of $180m/s$. The velocity with which bullet hits the thief car is,
A. $250m/s$
B. $450m/s$
C. $170m/s$
D. $150m/s$

Answer 1

To solve this question, we have to know about velocity. We know that the speed of an item is the pace of progress of its situation concerning an edge of reference, and is a component of time. Speed is comparable to a particular of an item's speed and heading of movement.

Complete step by step answer:
We can say according to the question that, the effective speed of a bullet is equal to speed of bullet plus speed of police jeep. Which is equal to, $180m/s + 45km/hr$
\Rightarrow 180 + 45 \times \dfrac{5}{{18}}m/s \\\ \Rightarrow 192.5m/s \\\
According to the question, the speed of thief’s jeep is equal to, $153km/hr$
Which is equal to $\dfrac{{153 \times 1000}}{{1 \times 3600}} = 42.5m/s$
Now, velocity of bullet with respect to thief’s jeep is equal to,
\Rightarrow (192.5 - 42.5)m/s \\\ \Rightarrow 150m/s \\\
So, the right option is $D$.

Note: We can forget to transfer the unit of the velocity of the thief’s jeep. We have to transfer km/s into m/s. otherwise this calculation will become wrong. We have to calculate all the values in the same unit. We have to keep this in our mind. The unit of velocity is m/s. and the unit we also know that, the unit of the acceleration is, meter per Second Square. These units are in the S.I unit. We have to calculate this very carefully in the same unit.