Question

Two trains are moving in opposite direction .train A moves east with a speed of 72km/h and train B moves west with a speed of 90km/h what is the-
(1) relative velocity of B wrt A?
(2) Relative velocity of ground wrt B?

Answer 1

1)-18km/h
2)72km/h

I am rithvik of class 10 is it correct

Answer 2

(1)162 km/h

(2)90 km/h

Explanation:

The relative velocity equation is:

$v_A_B = v_A - v_B$

Here $v_A_B$ is the relative velocity of the body A respect body B  and $v_A$ is the velocity of the body A  and $v_B$ is the velocity of the body B.

(1)Given v_A = 72 km/h and v_B = - 90 km/h

Both are moving opposite direction.

Therefore,

Relative velocity of B w.r.t  A= Sum of speeds of trains

$v_B_A=72km/h+90km/h$

      = 162 km/h.

Thus, relative velocity B with respect to A is 162 km/h.

(2)

Now relative velocity of ground wrt B,

$v_G_B=v_G-v_B$

as velocity of ground zero, so

$v_G_B=0-(90km/h)$

   =  90 km /h

Thus, the relative velocity of ground wrt B is 90 km/h.

#Learn More: relative velocity.

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