Asked by Gary
Is this logic correct?
Explain why momentum is conserved when a ball bounces off the ground.
My logic :
The ball strikes the ground with velocity v. As it leaves the ground, its velocity is also v but in the opposite direction.. i.e -v
Hence, m*v + m*(-v) = 0. So, momentum is conserved
Explain why momentum is conserved when a ball bounces off the ground.
My logic :
The ball strikes the ground with velocity v. As it leaves the ground, its velocity is also v but in the opposite direction.. i.e -v
Hence, m*v + m*(-v) = 0. So, momentum is conserved
Answers
Answered by
Damon
Well, sort of, but in fact momentum is not conserved in this collision.
The first law, conservation of momentum, applies ONLY if there is no external force.
That is not the case here.
The ground exerts a FORCE on the ball, changing its momentum from +mv to -mv
Force = rate of CHANGE of momentum.
What is conserved is kinetic energy.
The first law, conservation of momentum, applies ONLY if there is no external force.
That is not the case here.
The ground exerts a FORCE on the ball, changing its momentum from +mv to -mv
Force = rate of CHANGE of momentum.
What is conserved is kinetic energy.
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