Question

The freight cars a and b have a mass of 20mg and 15mg respectively.After collision,b moves to the with a speed of 2 m/s

Answer 1

answer is +3

__________

as mass is 20mg

speed = 2ms

Answer 2

See attached document for complete question.

We can use Newton's 2nd theorem to find impulsive force. That is,

average impulsive force = rate of change of linear momentum

$F = (mV -mU)/t$

Where, m = mass of a body

             V = last velocity of the body

             U = initial velocity of the body

             t = time

Now we can calculate impulsive force by using car 'B',

          m of B = 15000 kg

           V of B =2 m/s in right = ----> 2m/s

           U of B = -1.5 m/s in right = ----> -1.5 m/s

                    t = 0.5 s

$F = [15000*2 - 15000*(-1.5)]/0.5$

$F = 15000 (2+1.5)/0.5$

$F =52500/0.5$

$F = 105000 N$

Answer : Impulsive force = $F = 105 kN$