[Physical Science:] Finding Kinetic Energy

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Homework Help Overview

The discussion revolves around two physics homework problems related to kinetic energy, specifically focusing on calculating mass from kinetic energy and velocity, and determining kinetic energy from mass and velocity. The subject area includes concepts of classical mechanics and potentially relativistic mechanics.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to understand how to manipulate scientific notation and apply it to the kinetic energy formula. Some participants suggest using the classical kinetic energy equation, while others mention the need for a relativistic approach due to high speeds. There is a question about how to derive mass from kinetic energy when it is already provided.

Discussion Status

The discussion is ongoing, with participants exploring different methods to approach the problems. Some guidance has been offered regarding the use of classical versus relativistic formulas, but there is no explicit consensus on the best approach to take.

Contextual Notes

Participants express uncertainty about the application of scientific notation and the relevance of relativistic effects due to the speeds involved in the problems. There is also a mention of the original poster's confusion regarding the formulas and calculations.

Jessi
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Two homework problems I don't understand. :(

9. An alpha particle travels at 1.6 x 10^7 m/s. The kinetic energy of the particle is 6.0 x 10^-13 J. What is the mass of the alpha particle?

I think scientific notation is supposed to be used, so "1.6 x 10^7" is 16,000,000 and "6.0 x 10^-13" is .0000000000006, but I still don't know what to do with the numbers.

10. An electron with a mass of 9.0 x 10^-31 kg moves through a vacuum with a speed of 2.5 x 10^8 m/s. Find the electron's kinetic energy.

Again, I'm guessing "9.0 x 10^-31" is .0000000000000000000000000000009 and "2.5 x 10^8" is 250000000, so does that make the answer 2.8125 x 10^-14
 
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Kinetic Energy is found by the equation

K.E. = .5 *m* v^2

where m = mass and v = velocity
 
You may want to use the relativistic formula for the second case,though,it's roughly 83% of the speed of light...

Daniel.

P.S.And yes,please use scientific notation...Nobody will be willing to count the zeros...
 
I'm given the kinetic energy - how do I find the mass?

Dexter, I'm sorry..I didn't understand anything that you said. I don't think I'm familiar with the relativistic formula. I'm guessing what I did was wrong, then? :P
 
Okay,no problem,then don't use it.Use the classical one.Extract mass,knowing the KE and velociy.A mere division...

Daniel.
 

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