[comphappy]

Originally Posted by feilmeier

Let us get away from the mass of the robot times the gravity, and consider just the weight, since it comes in force measurements, and is much easier to calculate with.

Maximum Static Friction = Coefficient of Friction times the normal force/weight

If you increase the normal force, either by adding more mass, or by applying force in the form of a downdraft caused by a fan, then the Maximum Static Friction becomes larger. That's Algebra. 0.06 * 10 < 0.06 * 20

Now wheels that roll without slipping should ideally roll without friction, but as we all know, that's false. Rolling friction equals coefficient of friction times the normal force. This coefficient can also be the same as the one used in the static friction. As the tread touching the ground is at rest relative to the ground this makes it true.

If you can refute this, please point me to where you found this. I found all of my equations inside of Physics for Scientists and Engineers 5th edition, Extended Version page 118-127

Ah my friend you are oh so close, they do have friction the static friction. And yes the frictional force increases with mass, however it is harder to get a more massive object to move. As in my proof above you will see friction force down is proportional to the force to push the object (with out moving into dynamic friction ie slipping) across. All the forces are greater but only by the mass, they cancel. Its all the same until a collision. then its just p=mv with some lost to heat and deformation.