why is walking on pebbles more painful than walking on sand?

Question

It would be better if the answer reffered to pressure, force and area

Answer 1

The sand grains are soooo tiny that when you step on sand it creates like a mold around your foot so you're actually being cushioned by sand whereas pebbles are much more larger pieces of rocks that are uneven, some rocks may be larger than other rocks and are mostly found on streets or hard roads versus sand grains which are found at the beach where the earth is wet and soft. Sand's tiny grains surround your foot versus pebbles which can sometimes be sharp and some smooth and bigger. Hope I'm making some sense... I'd rather walk on sand.

Answer 2

Ok, this question has bee answered but i would like to make a more clear physicsy answer.

Lets assume pain equates to pressure (so if you put a large force on a small area it will hurt more than the same force on a large area because pressure = force/area)

The total force exerted on the entire bottom of your feet is the same when walking on both pebbles and sand, because the force is equal to your weight (mass x grav)

However, when you step on pebbles the force is not spread across the entire bottom of your feet, in fact it is concentrated on a much smaller area.

Remember we said that pain = pressure = force/area. This means a decreas in area will increase pressure, consequently inreasing pain.

I hope this clears things up for ya....

Answer 3

Deals with thickness of the skin on the bottom of your foot. Sand when you step on it will only indent the skin a small amount. The amount of weight of the person determines how painful the pebble with be. If you step on sand you indent the skin, but there is a layer of fat beneath the skin. You have sensory receptors in your surface layer of skin and each layer under there. Each additional layers sensory receptors alert the mind to the severity of intrusion. First layer is a hmmm...the second layer is an ouch...third layer is an oh my god that hurts. The pebble covers a small area bring focus to a small area and since the pebble is larger it will penetrate and intrude further reaching the inner layers of sensory receptors. The more focused the area the more intense the pain. The wider the area of receptors the less intense the pain.

Answer 4

You have answered your own question really havent you?
Sand is finer and therefore moulds to the shap of your foot and so the weight of your body is spread over the total area of your foot. With pebbles the contact area is less and therefore there is more pressure at the contact points.
It is the same for a bed of nails, put your hand hard on 1 nail and it will hurt, have 500 nails out of the same area then the force previously used is now spread around 500 points.

Answer 5

Pebbles are able to focalize the force that your weight puts on them while walking across them, and applies greater pressure to your feet than sand does. By the equation P = F/A, we see that a larger area (i.e. the collectively larger surface area of the sand exposed to your feet) causes diminished pressure to be applied to your feet, as a function of force (your weight), rather than walking on the edges of several pebbles, which applies much greater pressure in response to the same force (your weight), because of the relatively much-smaller surface area through which it is directed.

Answer 6

I can understand why pressure and force would influence the difference between walking on sand and pebbles, but area??? I'd say that pebbles are more painful because they're awkward to walk on due to their shape, and make walking imbalanced, difficult. Your feet just sink in deep sand no matter how much pressure you put on it. Sand is softer and moves to fit the shape of the object putting pressure on it, but pebbles don't.

Answer 7

It it because of the way that the weight of the person is distributed. over tiny, almost level sand the weight is distributed evenly. over pebbles the weight is concentrated on a few specific points. suppose a person weighs 150 lbs and the weight is distributes over several pebbles. it would feel like a pebble was being jammed into the bottom of your foot with a force equal to 150 lbs devided by the number of pebbled bearong the weight. which is why when we step on one thar is larger we notice it more.

Answer 8

It has to do with the pressure on your feet.
When you walk on pebbles, less of your foot is actually in contact with the ground. (ie the area is less)
Your downward force due to gravity stays the same

Since pressure= force/area
the pressure is greater.

Exactly the same way as the lady in stilleto heels exerts more pressure on the ground than an elephant does!

Answer 9

When a Fakir lies on a bed of nails, the nails are set very close together in order for the weight to be distributed over a large area as in walking on sand .... Much less painful. (Weight (Force) ÷ Area)

Have you seen a Fakir trying to lie on 2 or 3 nails as in walking on pebbles ?.

Answer 10

It is to do with the dispermant of weight. Sand is smaller than a pebble thus your weight is spread evenly across all of the sand,whereas pebbles are fewer and the weight is not evenly spread.

Just like the act of lying on a bed of needles. It doesn't hurt because your weight is evenly spread across all of the points.