A man weighing 70 kg runs alongside railroad tracks with a velocity of 18 km/h, and jumps into a car of weight 100 kg standing on the tracks.
Calculate the velocity with which the car and man will start moving.

7.4 km/h

Step-by-step explanation:

Since this involves momentum conservation, apply the principle of linear momentum.

The principle of linear momentum states that:

+ = ( + )V

where: is the mass of the man, is the velocity of the man,   is the mass of the car, is the velocity of the car, and V is the common velocity of the man and car.

But, since the car was initially at rest, = 0.

70 x 18 + 100 x 0 = (70 + 100)V

1260 = 170V

V =

  = 7.4118

V = 7.4 km/h

The car and man would start to move with a velocity of 7.4 km/h.

answer:      

step-by-step explanation: