- #1
silversurf
- 26
- 0
does anyone know why momentum is not conserved in this problem? I thought momentum was always conserved when no net force acted on the system? Is the ground considered the net force acting on the system? Even though it changes direction I was thinking momentum would still be conserved except that the ball would move in the opposite direction.
This is the question.
Which of the following quantities is (are) conserved when a falling object strikes the ground?
I.
Momentum of the object
II.
Kinetic energy of the object
III.
Total energy
Click here to view the periodic table
Correct Answer:
III only
Your answer: You were incorrect
I and III only
III only
Explanation
I.
Momentum of the object
II.
Kinetic energy of the object
III.
Total energy
Total energy (III.) is conserved when a falling object strikes the ground.
Since the object’s velocity drops to zero after the impact, its momentum certainly changes (eliminating I only and I and III only) and its kinetic energy drops to zero (eliminating II and III only). The total energy of a system (which includes heat) remains constant.
This is the question.
Which of the following quantities is (are) conserved when a falling object strikes the ground?
I.
Momentum of the object
II.
Kinetic energy of the object
III.
Total energy
Click here to view the periodic table
Correct Answer:
III only
Your answer: You were incorrect
I and III only
III only
Explanation
I.
Momentum of the object
II.
Kinetic energy of the object
III.
Total energy
Total energy (III.) is conserved when a falling object strikes the ground.
Since the object’s velocity drops to zero after the impact, its momentum certainly changes (eliminating I only and I and III only) and its kinetic energy drops to zero (eliminating II and III only). The total energy of a system (which includes heat) remains constant.