How Is Maximum Kinetic Energy Calculated for an Electric Bicycle with a Rider?

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Homework Help Overview

The discussion revolves around calculating the maximum kinetic energy of an electric bicycle carrying a rider. The problem involves parameters such as the mass of the rider, the bicycle, and the maximum speed, along with the distance the bicycle can travel before needing a recharge.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants explore different methods for calculating kinetic energy, including using the formula 1/2mv^2. There are questions regarding the relevance of certain parameters, such as the maximum speed and the distance the bicycle can travel, as well as the assumptions made about resistance forces.

Discussion Status

The discussion is active, with participants questioning the logic behind certain calculations and the relevance of provided information. There is no explicit consensus on the correct approach or interpretation of the problem, and multiple lines of reasoning are being explored.

Contextual Notes

Participants note the absence of vertical movement in the problem setup, raising questions about the inclusion of gravitational force in the calculations. There is also uncertainty regarding the relationship between kinetic energy and the total energy stored in the battery, as well as the implications of the distance the bicycle can travel.

Dongorgon
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Homework Statement



An engineer was to design a bicycle that can be powered only by an electric motor. The bicycle can carry an 80kg rider at a maximum speed of 6m/s. Under these conditions the maximum distance the bicycle can cover before the battery needs to be recharged is 32km. The bicycle has a mass of 30kg. Calculate the maximum kinetic energy of the bicycle and rider when the rider is not pedalling.


The Attempt at a Solution


Assuming that no resistance force acts, what I've done is to consider the work done as equal to the change in kinetic energy over the entire displacement.
From this: WD=110x9.8x32000=34496000J
Hence, KEmax=34496000J
Which also is the entire stored energy of the battery.
Is this a correct way, and would this answer be sufficient? Thanks
 
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You seem to have involved g somehow, but there's no mention of vertical movement. What's your logic for that?
OTOH, you have not used the info re 6m/s, which does seem to be highly relevant.
(Are there more parts to the question?)
 
Yeah, through working out the KE via 1/2mv^2 it obtains a value of 1980J. But for some reason, this seems far too small considering this energy can carry the rider 32km also? Would I be correct in thinking this value for KE is also the total energy stored by the battery?
Also, there are no more parts, just that. Thanks for the fast reply.
 
Dongorgon said:
Yeah, through working out the KE via 1/2mv^2 it obtains a value of 1980J. But for some reason, this seems far too small considering this energy can carry the rider 32km also?
The max KE is not the energy required to carry the rider 32km. That might be the case if all the energy in the battery were converted to KE straight away and thereafter it's just carried along by its KE. The reason I asked if there are more parts is that the 32km does not seem to be relevant. But it's not unusual for irrelevant information to be provided as a test of whether the solver can figure out what is.
 

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