You ’ve probably seen the headline : " Man pulls 50,000 - pound autobus with tooth . " It sound pretty impressive , but let ’s see how hard it really is to move the busbar .

assume the bus is on level solid ground , the main force that has to be overtake to move the jitney is the rolling resistance of the tire . This military unit depends on two things , the weight of the bus topology and the coefficient of rolling resistance of the tire . We screw the system of weights , but where does the rolling opposition come from ?

Thetireson any vehicle deform or squish as they move , and it takes force to make them deform . The less they change form , the less violence it admit . For instance , a train bike has less than one - tenth the resistance of a car tire because a sword bicycle does n’t deform as much as it rolls .

A big passenger vehicle has tires with a coefficient of rolling resistance of 0.006 - 0.01 . Making sure that the pressure in the tires is correct , or even a little bit in high spirits , can minimize the electrical resistance . So we ’ll say that for this stunt that coefficient is 0.006 .

This means that the force required to rend the bus is 0.006 multiplied by the weight of the busbar , or 0.006 times 50,000 pounds . That is 300 pounds . There might be some extra force from brake drag or friction in the driveline , so we ’ll say it takes 400 pounds of violence to move the bus .

This is a lot of force , but it is possible for a person to exercise this much personnel with his legs ( and hold it with his dentition ) . But the trouble now becomes grip . Just like the coefficient of rolling resistor , there is acoefficient of frictionbetween your shoes and the ground . This coefficient determines how much force you’re able to apply in the horizontal focusing before your feet slip . About the best coefficient you could hope for is 1.0 . If your shoes did have a coefficient of 1.0 , then you could apply a force play equal to your weight in the horizontal direction . Most in all likelihood though , the coefficient of friction would be less than 1.0 , so unless you weighed much more than 400 Sudanese pound , you would not be able to exert that much force against the ground .

So the second part of the bus - extract conjuring trick is to increase your traction . Sometimes the tugger do this by anchoring a run to the road and using the steps of the ladder to push against . If a man is pull a train , then he could advertise against the railroad ties . These methods make traction less important because now you are pushing against a upright surface alternatively of a horizontal one , so the force you apply against the ladder is in the same management as the force you apply against the bus . This make draw in the bus more like snarf a 400 - pound weight unit with your legs .

Your teeth have to be capable to hold the rope with 400 pound of force , but they do n’t do the lifting . You might be think that your cervix is the infirm link – how can your neck muscles plagiarize 400 pounds ? The answer is , you do n’t really face-lift the whole weight with your neck muscles . Since you have to list back a lot to bear on against the run for adhesive friction , most of that 400 pounds of force is transmitted down your spine . For instance , if you were lying prostrate on your back while you deplume the motorcoach , all of the 400 pounds of force would be transmitted down your spine . So the unaired you could get to the ground , the less wedge your neck muscles have to utilize .

pull the passenger vehicle is still an impressive feat , but lift 400 pound with your legs while holding it in your tooth sound a little less impossible than take out a 50,000 - pound sign autobus .

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