Question

analyze the collision of a baseball with a bat. during which portion of the collision does the baseballs velocity reach zero?
before the collision
one - hundredth of a second after the collision
one second after the collision
during the collision
when the net external force on a closed system is zero, it is described as
constant
motionless
an isolated system
a normal system

Explanation:

• For the first question: When a baseball collides with a bat, its velocity changes. Before the collision, it has a non - zero velocity (moving towards the bat). After the collision (even one - hundredth of a second or one second after), it has a new non - zero velocity (moving away from the bat). During the collision, as the bat exerts a force on the ball, at some instant within the collision time interval, the ball's velocity reaches zero.
• For the second question: By definition, a closed system with zero net external force is called an isolated system. A constant could refer to a constant value of a quantity (not the system description). Motionless implies zero velocity (but the system can have non - zero momentum if there are internal motions in a more complex sense). A normal system is not a standard term in this context.

Answer:

• First question: During the collision
• Second question: an isolated system