How Do You Calculate Change in Momentum Without Mass?

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Homework Help Overview

The discussion revolves around calculating the change in linear momentum of a ball dropped from a height, specifically focusing on the scenario where the mass of the ball is not provided. Participants explore the implications of this missing information in the context of momentum calculations.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the relationship between momentum and mass, questioning how to approach the calculation without knowing the mass. There is also a focus on the importance of sign conventions for velocity as the ball falls.

Discussion Status

Some participants have clarified that the problem asks for momentum per unit mass, leading to a discussion about whether this means that linear momentum equates to velocity. The conversation is ongoing, with different interpretations being explored.

Contextual Notes

There is a noted absence of information regarding the mass of the ball, which is central to the discussion. Participants are also considering the implications of sign conventions in their calculations.

amanda.ka
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Homework Statement


I did an experiment where I dropped a ball beneath a motion sensor and it recorded the vertical components of position vs time, velocity vs time, and acceleration vs time.
The question asks to determine the change in the ball's linear momentum (per until mass) during the 5 selected impacts with the ground. I know that the equation for linear momentum is p = (mass)(velocity) however the experiment did not say to weigh the ball so I do not have "m". How would I go about solving this? Also I know that momentum is a vector quantity so the sign is important. Does that mean my velocity values would be negative as the ball is falling towards the ground? Thanks in advance!

Homework Equations


p = mv

The Attempt at a Solution

 
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amanda.ka said:

Homework Statement


I did an experiment where I dropped a ball beneath a motion sensor and it recorded the vertical components of position vs time, velocity vs time, and acceleration vs time.
The question asks to determine the change in the ball's linear momentum (per until mass) during the 5 selected impacts with the ground. I know that the equation for linear momentum is p = (mass)(velocity) however the experiment did not say to weigh the ball so I do not have "m". How would I go about solving this?
Note that the problem didn't ask you for the momentum but the momentum per unit mass.

Also I know that momentum is a vector quantity so the sign is important. Does that mean my velocity values would be negative as the ball is falling towards the ground? Thanks in advance!
This depends on your sign convention. Which direction do you want to call the positive direction? If the ball's velocity is in that direction, it would be positive; if it's in the opposite direction, it would be negative.

Homework Equations


p = mv

The Attempt at a Solution

 
vela said:
Note that the problem didn't ask you for the momentum but the momentum per unit mass.

Does this mean that the linear momentum would just be equal to the velocity?
 
Yes, the momentum per unit mass is just the velocity.
 
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