# Physics

posted by .

1. What does it mean to say a physical quantity is conserved? Why is this idea useful? (I don't understand how it is useful)

-When a physical quantity is conserved it means that it doesnâ€™t change.

2. A 2 kg ball of putty moving to the right at 3m/s has a head-on inelastic collision with a 1 kg ball of putty moving to the left at 3m/s. What is the final magnitude and direction of the velocity of the stuck together balls after the collision?

-This is what I have and I am not too sure what to do next.

m1v1 +m2v2= (m1+m2)u2
(2kg)(3m/s) + (1kg)(3/s)= (2kg +1kg)u2

3.Name some quantities, other than momentum, that are commonly considered to be conserved. Explain what a conservation law is.

-Some other quantities other than momentum that are commonly considered to be conserver are energy, mass, and matter. A conservation law is where the measurable property of an isolated physical system does not change as the system evolves.

• Physics -

The idea of conservation means one can look after a reaction or event, and the conserved quanity is unchanged (mass, charge, etc)