Quote:
Originally Posted by comphappy
So with no wind propulsion which I said in my first response. mass does not mater in terms of acceleration.
This is important to make clear as intuition for most people is wrong here.
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This is not entirely true. It is true that if you're only accelerating the robot, then mass doesn't matter. But you're also accelerating a ~40 lb trailer behind your robot. It will add some additional normal force to your robot, but, only a fraction of its total weight, as it's not resting entirely on your robot. So, briefly, assuming a third of the trailer weight is on your robot:
Code:
120 lb Robot 60 lb Robot
mr = 120 lbs ~= 55 kg mr = 60 lbs ~= 27 kg
mt = 40 lbs ~= 20 kg mt = 40 lbs ~= 20 kg
Fr = 55 kg * 9.8 m/s2 Fr = 55 kg * 9.8 m/s2
Fr = 539 N Fr = 264.6 N
Ft = 20 kg * 9.8 m/s2 Ft = 20 kg * 9.8 m/s2
Ft = 196 N Ft = 196 N
Fn = Fr + Ft/3 Fn = Fr + Ft/3
Fn = 604.33 N Fn = 329.93 N
Ff = Fn * u Ff = Fn * u
Ff = 36.26 N Ff = 19.796 N
a = Ff/(mr + mt) a = Ff/(mr + mt)
a = .48344 m/s2 a = .42119 m/s2
So, because of the trailer, mass does matter to your overall acceleration, barring windage, etc. By decreasing the relative proportion of the dead weight of the trailer, you actually increase your effective acceleration. And this isn't accounting for any frictional effects from the trailer, as well.