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Which would be easier to push in a straight line, a flat cart with 4 wheels or the same cart (and same load) with the same size wheels, but has six wheels? and why? Thanks

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  • $\begingroup$ the additional wheels would add extra weight, maybe you mean the total weight (cart + wheels + load) being equal $\endgroup$ – Nikos M. Oct 24 '14 at 19:02
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    $\begingroup$ Perhaps a slightly different question: under what conditions does a 6 wheel cart become more efficient than a 4 wheel cart? $\endgroup$ – Dan Bryant Oct 24 '14 at 19:47
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    $\begingroup$ Basically just a rehash of: physics.stackexchange.com/questions/93073/… Almost a duplicate? I'm not entirely sure though. $\endgroup$ – tpg2114 Oct 24 '14 at 20:05
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    $\begingroup$ Perhaps a better vehicle for reasoning would be to compare advantages of a four-wheeled vehicle vs a similar weight "infinite-wheeled" vehicle, i.e., tracked vehicles. 4 wheels get lower rolling resistance on hard surfaces, but many wheels deform the surface less (and thus require less work overcoming it) if it's soft and deformable, i.e. sand or mud. $\endgroup$ – Peteris Oct 24 '14 at 20:54
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    $\begingroup$ This is kind of a silly question. Depending on the circumstances and how you parameterize it, the optimum could be one wheel or 100. There is no inherent reason why one configuration would be better than another in the general case, only when you specify conditions (soft soil, rough ground, differences in bearing friction, etc) that will favor one choice over another. $\endgroup$ – Hot Licks Oct 25 '14 at 2:11
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Where more wheels becomes an advantage that can make mobility easier is in reducing ground pressure. On non-deformable surfaces like paved roads or hard packed soil this doesn't matter for mobility; but in softer soil or mud the lower ground pressure reduces the likelihood or severity of sinking into the soil reducing the risk of getting stuck and the amount of energy lost pushing soil around even if not.

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  • $\begingroup$ But that's as much a matter of wheel size and total ground contact area as anything. One large wheel or 100 tiny ones would work out about the same. $\endgroup$ – Hot Licks Oct 25 '14 at 2:07
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It would be easier to pull the car with 4 wheels because you would need less energy to make only 4 wheels move (less angular momentum).

What I'm saying is that its harder to accelerate and stop the cart with more wheels, but to make it keep his velocity, the force is actually the same because the attrition is the same with both 4 or 6 wheels. It only depends on the weight of the cart and the materials used.

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  • $\begingroup$ all things being equal, 4-wheel cart being easier is more plausible (as you mention extra ang. momentum, initial inertia etc..) $\endgroup$ – Nikos M. Oct 24 '14 at 19:04
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Throwing in my two cents.

The reason large trucks which travel on hard surfaces have more than four wheels is so that the axles don't break.

The weight is distributed over 3+ axles rather than just two.

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    $\begingroup$ And so the road doesn't break. $\endgroup$ – Loren Pechtel Oct 25 '14 at 0:39

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