Pool Ball Impulse: Calculating Speed After Impact

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Discussion Overview

The discussion revolves around calculating the speed of a pool ball just after being struck by a cue stick, given the average force applied, the duration of the impact, and the mass of the ball. The context includes elements of physics related to impulse and momentum, as well as potential homework-related inquiries.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant requests assistance in calculating the speed of a pool ball after being struck, providing specific values for force, time, and mass.
  • Another participant suggests that the force and mass can be used to calculate the acceleration, which can then determine the speed at the end of the impact period, while noting the importance of the timing of the measurement.
  • A third participant mentions the relationship between change in momentum and impulse, indicating that impulse can be calculated as force multiplied by time.
  • One participant shares a personal anecdote about their experience in pool but expresses uncertainty regarding the problem, suggesting it may be more intuitive than calculative.
  • A final participant references Newton's equations of motion, indicating a method to substitute values to find the solution.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the approach to the problem, with some focusing on mathematical calculations while others express uncertainty or offer anecdotal insights. The discussion remains unresolved regarding the specific method to calculate the speed.

Contextual Notes

There are assumptions regarding the interpretation of "just after impact," which may affect the calculations. Additionally, the discussion does not clarify the exact steps needed to arrive at a solution, leaving some mathematical processes unresolved.

alanm
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Hi All,
can some one please help with this.

a cue stick strikes a stationary pool ball with an average force of 51N over a time of 12ms. the ball has a mass of 0.22kg, what speed does the ball have just after impact/

I am struggling with this.

thanks
 
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alanm said:
Hi All,
can some one please help with this.

a cue stick strikes a stationary pool ball with an average force of 51N over a time of 12ms. the ball has a mass of 0.22kg, what speed does the ball have just after impact?

If this is a homework question, this post should go over in the homework section. But with that said...

The force and the mass are sufficient to calculate the acceleration of the ball as the cue stick applies force to it. You know how long the acceleration lasts, and that will allow you to calculate the speed at the end of the acceleration.

(Note that this answer assumes that by "just after impact" you mean just after the impact is finished, at the end of the 12 ms period. If you mean just after the start of the impact when the cue stick first touches the ball at the beginning of the 12 ms period, then the answer is "zero because the ball is still stationary", just about to start moving. Only an evil professor with a wicked sense of humor would pose such a deceptive trick question... but such do exist).
 
You're probably supposed to use the fact that change in momentum = force x time (impulse).
 
Wow! I played in the world finals in Las Vegas 5 years in a row, and I have no idea as to your problem. It's just something that you feel.
 
Newton and the equations of motion..

f=ma
v=u+at

substitute.
 

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