Calculating Horsepower/Torque from Acceleration/Mass

  • Thread starter Sentient
  • Start date
  • #1
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Apologies in advance if this is not the correct forum.

This is (what seems to me) an old question people have been playing with for a while, but I dont seem to be able to figure out where I have gone wrong.

Could someone point out the mistake in my math from the following example:

Constant Mass = 1180Kg

Sample 1 @ 2 secs
Kilometers/Hour = 37
Meters/Sec = 10.278
RPM = 3000

Sample 2 @ 3 secs
Kilometers/Hour = 46
Meters/Sec = 12.778
RPM = 3780

Sample 3 @ 4 secs
Kilometers/Hour = 59
Meters/Sec = 16.389
RPM = 4860


Using the formula: KE = (1/2)(m)(v^2) I calculated

KE1 = 0.5 * 1180 * (10.278 * 10.278) = 62326 ??Joules??
KE2 = 0.5 * 1180 * (12.778 * 12.778) = 96333.6 ??Joules??
KE3 = 0.5 * 1180 * (16.389 * 16.389) = 158473.6 ??Joules??

Using the formula: W = (KE / Time) given the sampling time is 1sec
W = KE.

Converting (roughly) from W (watts) to HP: HP = W / 746

HP1 = 83.54
HP2 = 129.12
HP3 = 212.32

I know from another piece of software that the correct values should be:

HP1 = 59
HP2 = 76
HP3 = 105


Could someone be kind enough to point out my fault. Greatly appreciated.

Tony
 

Answers and Replies

  • #2
Hootenanny
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Could you start by stating the question exactly as it is given please.

~H
 
  • #3
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The question is:

Plot a graph showing horsepower at given time intervals based on sampled data.


There are actually 10 samples, but I have only included 3 for simplicity. The original data only included Time, Kilometers/Hour and RPM (although I don't think RPM is needed for this part of the question). I converted KPH to meters/sec as I think this is the correct unit for KE.
 
Last edited:
  • #4
Hootenanny
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And you have no other information regarding the vehical?

~H
 
  • #5
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I was given the vehicle weight of 1180kg, and the time-sampled data, but nothing else.
 

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