a 20000kg railroad car is rolling 6.00m/s when 7000kg olaf id gravel is suddenly dropped in. What's the cars speed after gravel is loaded?

The cars speed after the gravel is loaded, V = 4.44 m/s

Explanation:

Given data,

The mass of the railroad car, m = 20000 kg

The velocity of the railroad car, v = 6 m/s

The mass of the dropped gravel, m = 7000 kg

The momentum of the railroad car,

P = mv

= 20000 x 6

= 120000 kg m/s

According to the law of conservation of momentum,

P = V (M + m)

V = P / (M + m)

= 120000 / (20000 + 7000)

= 4.44 m/s

Hence, the cars speed after the gravel is loaded, V = 4.44 m/s