Calculating Horsepower/Torque from Acceleration/Mass

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SUMMARY

The discussion focuses on calculating horsepower and torque from acceleration and mass using kinetic energy formulas. The user provided a constant mass of 1180 kg and three samples of speed data over time, calculating kinetic energy (KE) and subsequently horsepower (HP) using the formulas KE = (1/2)(m)(v^2) and HP = W / 746. However, the calculated horsepower values (HP1 = 83.54, HP2 = 129.12, HP3 = 212.32) differ significantly from expected values (HP1 = 59, HP2 = 76, HP3 = 105), indicating a potential error in the calculations or assumptions made regarding the time intervals and conversion factors.

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  • Understanding of kinetic energy calculations
  • Familiarity with horsepower and watt conversion
  • Basic knowledge of physics related to mass and acceleration
  • Ability to interpret speed data in different units (KPH to meters/sec)
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  • Review the principles of kinetic energy and its application in automotive physics
  • Learn about the relationship between acceleration, force, and horsepower
  • Investigate the impact of time intervals on power calculations
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Automotive engineers, physics students, and anyone interested in vehicle performance metrics will benefit from this discussion, particularly those involved in calculating and analyzing horsepower and torque from acceleration data.

Sentient
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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 don't 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
 
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Could you start by stating the question exactly as it is given please.

~H
 
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:
And you have no other information regarding the vehical?

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

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