Hi, I need help calculating the volume of an irregular shape?

Question

Specifically, some rocks for a science project, im trying to determine how much energy it would take to hurl these rocks a certain distance. But thier all different shapes and I only measured thier 3 major axis' ???????? Thank you!

I guess its worth it to mention that these are boulder sized rocks, i cannot put them in water to measure the displacement...

Thanks for all your answers so far, but when I mean boulder size I mean, stuck in the ground and imovable, like the size of a car... and regarding not needing to know the volume for my energy calculations, how else would i determine the rocks mass? the density is known, so far thats all i know for the density= mass/volume eq.

Answer 1

I can't imagine this being an EXACT science project, heaving boulders some distance! So... if you can't move these things without the use a bulldozer or crane, just guestimate (the best you can) the dimensions you can take, and approximate it using known volumes such as spheres, cubes ect ,kind of like taking a three-dimensional Riemann sum, only you are measuring the rock instead of divinding it up into subintervals. Don't think to hard about this!

Even if you were to get the EXACT volume, your still going to have to figure out drag coefficients and internal friction in the machine to get an exact distance. So this is more a trial and error thing like most engineering turns out to be.

Answer 2

If you no longer have access to the rocks (for example, if they were part of a lab you did and you can't go back and look at them again) there is no way to calculate their volume without more information. You cannot calculate the volume of an irregularly shaped object based only on measurements along the objects axes.

If you do have access to the rocks, you can drop them into water and measure the volume of water they displace. This is most easily accomplished in a graduated cylinder or similar device. Fill it partway with water and measure the initial volume of the water (read the reading on the side of the container). Then, drop in one of the rocks and record the new volume of water in the container. The volume of the rock is the new volume minus the old volume. Repeat this with each of the three rocks.

However, unless you are considering air resistance or some kind of friction in your calculations, you shouldn't need the volume of the rocks. In this case you only need the mass to calculate the amount of energy needed. You'll need to calculate the projectile path of the rocks along some arbitrary arc (perhaps shot at a 45 degree angle to the horizontal). You can use kinematics to calculate how fast the rock needs to be moving to travel a certain horizontal distance in the time it takes the rock to rise and fall. At a 45 degree angle to the horizontal, the rock will travel twice as far horizontally as it does vertically (because half of the horizontal distance will be spent going up, and the other half coming back down). You can then use the information you gain from the kinematics equations to calculate the amount of kinetic energy required. This would require the mass of the rocks, but not the volume.

Answer 3

The easiest way to measure the volume of an irregular object is to fill a bowl to the top with water and have that bowl inside of a larger bowl. Gently drop the rock into the inside bowl and an amount of water will overflow into the larger bowl. Remove (carefully) the smaller bowl with the rock inside and the volume of the water that spilled into the larger bowl will equal (approximately) the volume of the rock!
P.S. To determine how much energy it will take to hurl them a certain distance, mass is much more important that volume, assuming wind resistance is negligible.

Answer 4

Get a big beaker with clear marking on the side. (try a 500ml to 1000ml beaker that the rocks will easily fit into) Fill the beaker halfway. You might have to fill it more depending on how big the rocks are. The point is that when you put the rock inside the partially-filled beaker, the rock should be completely underwater yet the water should not overflow and leave the beaker. Now take out the rock. First write down how much water is inside before putting in one rock. Then put in one rock. Then write how much the level is now with the one rock inside. Subtract the two amounts and the resultant is the VOLUME of the one rock.

Peace

Answer 5

Weigh each rock, then calculate the mass density of each rock (given that you know their chemical makeup), and divide the mass by the density and the volume pops out.

Answer 6

Get a beaker or graduated cylinder and place them in it, measure the water it displaces. I would suspect mass would be more important than volume in this case though.

Answer 7

get a graduated cylinder wide enough to fit the rocks in and fill it to 50 mark with water. put the rock in and measure where ti goes to (pretend its 74) that means the rock is 24 milliliters, which is the same as a cubic centimeter

Answer 8

drop them into water
get a beaker or a cup with measurements of volume on the side and fill it half-way...drop the rock in it and the amount of water is displaces is how much volume it has
:)

Answer 9

Well you've come to the right place. You can't find a shape more irregular than mine.

Anyway, I can't calculate the volumn of my irregular shape, or yours either, but maybe the link below will help.

Answer 10

dip them in water and see how much water they displace