Does it require more or less effort to push a loaded wheelbarrow over hard level ground than to turn around and pull it? What about when the ground is soft?
鈥� There is little difference in effort in pushing or pulling over hard ground. Pushing is normally preferred as it is ergonomically favourable and the handles less likely to slip from your hands. The forces involved in moving a wheelbarrow over soft ground are more complex, involving a rotational force to lift the wheel over, or through, mud and gravel.
Consider a wheelbarrow pushed against a kerb. The force required to push over it depends on the relative heights of the kerb and the wheelbarrow鈥檚 axle. The force must be applied to the axle at a forward and upward angle. If the kerb is higher than the axle, it is impossible to push over it, which is why larger wheels work better.
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But by pulling the barrow, you can raise the handles and easily apply an upward force to successfully negotiate the kerb.
Sand, mud or gravel can be imagined as a series of micro-kerbs where pulling is more efficient than pushing, as anyone trying to push a heavy wheelie-bin over such surfaces will find.
David Muir, Edinburgh, UK
鈥� The horizontal force that must be applied to move the wheelbarrow is a function of the load and friction. The force required when pushing or pulling would be unchanged if it was applied at the centre of the wheel, but that isn鈥檛 the case here.
A wheelbarrow鈥檚 handles are much higher than its wheel. Using the handles to push it results in a force vector that resolves into a horizontal force, but also a vertical, downward force at the wheel. This adds to the apparent load, increasing friction.
Pulling the wheelbarrow instead reverses the force vector, so the vertical component is now an upward force, offsetting some of the load, and reducing the horizontal force required. This reduction in apparent load is why it is easier to pull, rather than push, a loaded wheelbarrow over an obstruction such as a kerb.
鈥淧erhaps the best answer comes from observation. Doesn鈥檛 almost everyone push, rather than pull?鈥�
Based strictly on the physics, it would seem pulling would always require less effort, especially on soft ground or over obstructions. Certainly a pushed wheelbarrow is easier to control, and to keep from tipping. Perhaps the best answer comes from simple observation. Doesn鈥檛 almost everyone push, rather than pull?
Howard Bobry, Nehalem, Oregon, US
鈥� The extreme case is trying to push a wheelbarrow over a kerb. It is almost impossible, whereas pulling it uses the effort advantage to help lift it over.
An additional factor is that when pushing, effort has to be put into holding one鈥檚 arms ahead to prevent walking into the barrow, whereas when pulling it, the arms can be more relaxed. Just make sure the barrow is well designed. Badly placed braces can cause havoc with your ankles!
David Jackson, Liverpool, UK
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