# Help With Acceleration Formula

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I've been on this for a few days now. Every time that I think I've got it solved I test it. Every time it fails miserably. I know the basic calculation for acceleration... Acceleration=Torque/Mass This returns the rate of acceleration in Meters per second squared. I also know the Aerospace Engineering formula for HP(although I'm not sure it's backwards compatible to effectively calculate torque).... HP=Torque*RPM*6.28/33000 Here is the last formula that I came up with... torque=horsepower/rpm*5252; accel=((torque/weight)/0.3058)//get acceleration into feet per second accel=accel*(finalDriveRatio-gearRatio[currentGear])//apply gear ratio I just can't find an efficient way to do this. If someone could help me get on the right path it would be GREATLY appreciated! [Edited by - apts08 on November 22, 2008 2:31:55 AM]

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Not sure what else is wrong, but IMHO there is at least the following problem.

When looking at SI units, we see that
unit of acceleration: [a] = m/s2
unit of force: [F] = kg*m/s2
unit of torque: [T] = kg*m2/s2
unit of power:

= kg*m2/s3

Acceleration=Torque/Mass
for the units on both sides, we get
m/s2 on the left (as you expected in the OP)
kg*m2/s2/kg = m2/s2 on the right
so there is a discrepancy. In fact, you mixed up torque (rotational) and force (linear), and hence don't compute linear acceleration but angle acceleration.

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I don't know anything about the lower equations, but I think the first equation you want is:

angular acceleration = Torque/moment of inertia
acceleration = angular acceleration*(distance of point in question from the axis of rotation).

Mass and moment of inertia are a bit different in that moment of inertia takes into consideration the distribution of mass about the rotation point. Wikipedia should be able to supply you with the formulas to get moment of inertia from mass and shape.

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