A truck always has more inertia than a roller skate.
Does a truck always
have more momentum than a roller skate?
yes
no
The total momentum of an isolated system of objects is conserved
only if conservative forces act between
the objects or
regardless
of the nature of the forces between the objects.
A ping-pong ball moving forward with a momentum p strikes and bounces
off a heavy bowling ball that is initially at rest and free to move.
The bowling ball is set in motion with a momentum
greater than p,
less than p, or
equal to p.
Ralph asked me a question about today's reading assignment. Suppose he
is floating in outer space with no forces acting on him. He is at rest,
so his momentum is zero. Now, he throws a ball. The ball goes one
way, and he goes the other way. Before the collision, there was no momentum,
and after the collision, there is plenty of momentum. He has momentum, and
the ball has momentum.
It certainly doesn't look like zero momentum, so it doesn't
look like momentum was conserved. How would you answer Ralph?