More friction questions

[Woody1458]

We did a few rover wheel robot tests today and based on what I saw I am puzzled. It appeared that a lighter robot would accelerate faster then a heavy robot. Lets see if I can throw out some formulas

Heavier
533.8 N (120 lbs) (54.47 kg on earth) robot
Ff= µ • Fn
x = .05 • 533.8
x= 26.69 N
a=F/m
.4899 m/s^2 = 26.69 N / 54.47 kg

Lighter
400.3 N (90 lbs) (40.82 kg on earth) robot
Ff= µ • Fn
x = .05 • 400.3
x= 20.02 N
a=F/m
.4904 m/s^2 = 20.02 N / 40.82 kg

In standard units, the lighter robot will accelerate 0.0164 ft/s^2 faster.

Based on these numbers, unless I did something wrong, a lighter robot would accelerate faster on regolith then a heavier one (admittedly a small difference). So teams that are talking about adding weights to their robot to add friction should reconsider.