# Conservation of momentum

Every year, the physics tutor fields a few questions on conservation of momentum.  It’s an interesting phenomenon because you can use it to explain some familiar, everyday situations.

Momentum is mass times velocity.  Something that is 50 kg, traveling at 12 m/s, has a momentum of 600 kgm/s.  It’s a vector, so two momentums can cancel each other out if they have opposite directions.

One great example of conservation of momentum is how a jet boat works.   The motor takes water, which has an initial momentum of zero, and pushes the water, giving it velocity.  The momentum the water gains needs to be canceled somehow, since total momentum must remain constant.  That’s why the boat goes forward:  to cancel out the backward momentum the water has been given.  The boat gains the same momentum forward that the water gains backward.  From the point of view of physics, that’s why a jet boat moves forward.

Thanks for dropping by, and come again!

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.