BOX PUSHING AND PULLING
mechanics
Description of the device
In both cases moving the box requires more effort than keeping it moving. When the box is still, static friction occurs. Its value is higher than that of dynamic friction, which occurs when the surfaces move relative to one another.
Phenomenon
Force is a vector quantity. This means that to describe it fully, it’s not enough to give only its magnitude (as you would do e.g. for mass), but the direction is also important. The box’s handle specifies distribution of forces in pushing, as well as in pulling. Force that we use while pushing the box may be expressed by two different forces, one of which is directed downwards, increasing the box’s pressure on the base, therefore increasing friction. While pulling the box one of the forces is directed upwards, which decreases pressure on the base and therefore decreases friction.
How to use it
Try to push the box while holding the handle. Can you move the box? Then try to move it by pulling on the handle. Do you feel the difference? Notice that in both cases setting the box in motion is the hardest, keeping it moving is a little easier.