[josinkjames]

Mass of objects are very less.It never hurt ,when it fall on us.science says that object have no weight in air(not in ground).we know that greater weight hurts us.
So it is cleared that weight is the reason for that we getting hurt,but science says that objects have no weight,so why we get hurt?? plaese help.

[ebaines]

We need to be a bit more specific about what is doing the "hurting" here. An object with a lot of weight can indeed hurt you more than an object with little weight, as it mat crush you - consider the difference between being stepped on by an elephant versus a small kitten. But objects of small weight can also cause hurt and pain: consider for example a bullet, which weighs only a few grams yet kills because of its great speed. The important factor here is the object's momentum, which is a term we use to describe an object's inertia. Momentum is equal to the objects mass times its velocity, and the larger the momentum the more damage it can cause. Note that the momentum involves the object's mass, not its weight - thus an object in orbit about the Earth is "weightless," but it may have a lot of momentum and can cause a lot of damage if it hits something, such as an astronaut or another satellite. Or to use your example - an object that floats in water (like a submerged submarine) has a lot of mass, and therefore if its moving it has a lot of momentum. Even though if you put the submarine on an underwater scale its weight would read zero, if it ran into you or another ship its momentum would cause great damage.