Calculating starting/tractive force

[snwright]

Hey all-

First post here!

I need to calculate the force required to overcome inertia of a 1500lb object. It's a sliding door, which rolls on 4 identical wheels, each with a coefficient of friction of .02. I'd like to make it accelerate to .25m/s over a period of 4 seconds.

I think what I need OMITTING FRICTION is: F=Ma = 6672 N * .0625m/s2 = 417 N = 93.74 lbs. Is that accurate? How do I include the resistance due to friction?

thanks!

Spencer

 

[obafgkmrns]

Resistance due to friction is weight of door times coefficient of friction. You need that much additional force. Be careful about how you consider the four wheels.

 

[snwright]

How should I be considering them? The load should be distributed pretty evenly across all four wheels. I was thinking that it would be a wash, and that the accumulated drag would be .02.

 

[jack action]

You need to add all the resistance forces to the inertia. The force needed would be:

F = 0.02mg + ma = m (0.02g + a)

g is 9.81 m/s² and the SI unit for m is kg not N (So 1500 lb is 680 kg). F = 176 N = 40 lb.