Pro asked in Science & MathematicsPhysics · 9 years ago

# Why do objects of same mass but different density float/sink on water?

Why is the effect of the upthrust different?

Relevance
• 9 years ago

If you take an object 6' x 6' weighing 10lbs, and lay it upon your body, then it would do no damage to your body and you would be able to remove it at will. However if you take a threading needle weighing 10lbs and it is tip down on your body, then it would penetrate your skin with you able to do nothing. It's not about the weight of the object. Both of these objects were the same weight. It all comes down to density. Approximate density of water is 1. If another object has a higher density, then it weighs more than water per molecule. So... it sinks.

The upthrust never changes. Only the down-thrust. If the down-thrust is 50 and the upthrust is 55, then when placed into water the object would rise slowly. If the down-thrust is 5 and the upthrust is 55, then when placed in water the object would rise quickly. Thus, making it appear as if the upthrust had changed though, it hadn't. Down-thrust is calculated by the objects mass, density, and gravitational pull.

Sorry if this is difficult to understand, I was kind of rushed...

Source(s): My own knowledge.
• Harry
Lv 6
9 years ago

time to do some research...that's what Mickey Mouse would say...