Adarsh
Last Activity: 6 Years ago
In 1st case there will not be any change in the speed of cart because momentum of boy is unchanged after jumping..
In 2nd case we will conserve momentum, 2 x (60+20) = 20 x v => v = 8m/s..
In 3rd case we will again conserve momentum , 2 x (60+20)=60 x 4 + 20 x v => v= -4m/s.. here negative sign shows the direction will be opposite to the initial direction...