How high does the ball rebound?

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Homework Help Overview

The discussion revolves around a physics problem involving a rubber ball that is dropped from a height of 2.0 m and its subsequent rebound. The original poster is specifically seeking assistance with determining how high the ball rebounds after hitting the floor, having already addressed earlier parts of the problem.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to calculate the rebound height using the change in momentum and velocity derived from previous parts of the problem. Some participants suggest focusing on the actual speed of the rebounding ball rather than the change in speed.

Discussion Status

The conversation is ongoing, with participants providing insights on how to approach the rebound height calculation. There is an emphasis on clarifying the relevance of the graph and the impulse involved in the problem, particularly for the specific question about rebound height.

Contextual Notes

The original poster has indicated that they only require help with the final part of the problem, having already solved the earlier questions. There is a mention of a graph that is not visible to all participants, which may affect the discussion.

edr2004
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I ONLY NEED HELP WITH LETTER G. I ALREADY HAVE THE CORRECT ANSWERS FOR A-F.
I posted all of the questions so you guys can see all the information I have.

Homework Statement



A rubber ball with a mass of 200 g is released from rest from a height of 2.0 m. It falls to the floor, bounces, and rebounds. The graph at right depicts the magnitude of the upward normal force that the floor exerts on the ball at various instants in time. The graph only shows the narrow window of time surrounding the interval when the ball was in contact with the floor.

a.) How long does it take the ball to fall the 2.0 m to the floor?
b.) How fast is the ball traveling just before it hits the floor?
c.) What is its momentum just before hitting the floor (using a coordinate system in which the positive-y axis points in the upward direction)?
d.) What is the impulse on the ball by the floor during the 10 ms the ball is in contact with the floor?
e.) What is the impulse on the ball by the earth’s gravitational pull during the same 10 ms?
f.) By how much does the ball’s momentum change as a result of this 10-ms period?
g.) How high does the ball rebound?


Homework Equations


Change of momentum = mass * change of velocity
V2^2 = 2a*change of position


The Attempt at a Solution


Change of velocity = (2.4kg.m/s) / (0.2kg) = 12m/s
(12m/s)^2 = 2 (9.81m/s2) * change in position
CHange in position = (144m2/s2) / 2*9.81m/s^2 = 7.34m , which is not correct.
Also I was able to calculate Acceleration from the impulse on ball by the floor. I am not sure if and/or how I would use that acceleration.
Anyway I would appreciate any help.
 
Last edited:
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I do not see your graph.
 
I attached the graph (it will open as a Word document). For some reason I can't paste it with my message.
 

Attachments

First things first. Answer a, b, & c: those question have nothing to do with your graph; treat the ball as any other falling body. The graph is only relevant for answering d. (For that you'll need the definition of impulse.)
 
Thanks for replying but again I ONLY NEED HELP WITH G, which asks how high the ball will rebound. I already have the correct answers for a-f. I only posted the other questions so you guys would know what information I was given. So if you could look under my orignal post at the attempt to solve the problem and offer some suggestions I would appreiciate it.
THANKS
 
Next time BE CLEARER. :smile:

edr2004 said:

The Attempt at a Solution


Change of velocity = (2.4kg.m/s) / (0.2kg) = 12m/s
(12m/s)^2 = 2 (9.81m/s2) * change in position
CHange in position = (144m2/s2) / 2*9.81m/s^2 = 7.34m , which is not correct.
Find the actual speed of the rebounding ball, not its change in speed. (You can use the results of f to find that rebound speed.)
 

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