Question

The mass of a truck with its cargo is 1800 kg. The truck is coasting to the right with a speed of 10 m/s. As it coasts its cargo of mass 300 kg is lifted up out of the truck by a crane. What will the velocity of the truck be after its cargo is taken off?

Answer 1

Here we apply conservation of linear momentum. The momentum of the truck with cargo and without cargo remains constant. That is,

$mv=m'v'$.

Here $m,v$ are initial mass and velocity. $m',v'$ are final mass and velocity. Here $m=1800,v=10$ and $m'=1800-300=1500$.

The velocity of the truck be after its cargo is taken off is

$v'=\frac{mv}{m'} \\ v'=\frac{1800*10}{1500} \\ v'=12 m/s$

Answer 2

I would round it out to be 15 ms or 20 good luck