A Ball Is Thrown Vertically Upwards, Find The Ratio of PE to KE

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A ball of mass 65 g is thrown vertically upwards with an initial speed of 16 m/s, and the task is to find the ratio of potential energy (PE) to kinetic energy (KE) at half the time to maximum height. The calculations initially led to an incorrect ratio of 1:1, but the correct ratio is 3:1. Key errors included misapplying the signs for gravitational acceleration and misunderstanding the speed of the ball at the specified time. It was clarified that at t/2, the speed is not 16 m/s but rather half of the initial speed due to the effects of gravity. The discussion emphasized the importance of maintaining symbolic representation in calculations to avoid errors.
  • #31
haruspex said:
William, I know you are keen to be very helpful to the posters, and no doubt they are grateful, but the way the homework forums work is that we do not post complete solutions (unless the poster has already found one). We ask questions, provide hints, point out mistakes. In the long term, we believe this is of greater benefit.
yes, I totally understand, but OP was lost after a week of help; and the help was getting more an more abstract.

One piece of helpful advice was "Note that the answer is independent of g, m and u and, in fact, there was no need for any numerical calculations"

Which, is totally useless for somebody that is lost. Why is the answer independent? Why is there no need for calcs? There was no explanation. That was just left there, hanging. Fine if you are au fait with projectile motion - utterly bewildering if you are not. If the OP was already lost, this "smart" help help just made them even more lost!

Surely there is a point where somebody needs to be shown how to do something so they can move forwards? I know that is certainly true for me - especially after a week of frustration trying to figure something out! Isn't that what teachers do?
 
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  • #32
William White said:
yes, I totally understand, but OP was lost after a week of help; and the help was getting more an more abstract.

One piece of helpful advice was "Note that the answer is independent of g, m and u and, in fact, there was no need for any numerical calculations"

Which, is totally useless for somebody that is lost. Why is the answer independent? Why is there no need for calcs? There was no explanation. That was just left there, hanging. Fine if you are au fait with projectile motion - utterly bewildering if you are not. If the OP was already lost, this "smart" help help just made them even more lost!

Surely there is a point where somebody needs to be shown how to do something so they can move forwards? I know that is certainly true for me - especially after a week of frustration trying to figure something out! Isn't that what teachers do?

@William White I can't say I'm happy with this unsolicited abuse. If you're unhappy with what someone else has said to you, then leave me it of, mate!
 

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