Why Newtons Third Law doesn apply when the object is sinking?
Hello Kok Gheng, Newton’s Third Law does apply. There are actually several forces involved while the object is sinking. The earth attracts the object with a force, the weight, and the object attracts the earth with an equal and opposite force. The earth is also attracting the water around the object. The object exerts a force on the water it is falling through (that’s why the water gets out of the way). And the water exerts a force on the object, this force indicates its reluctance to get out of the way. There are 2 components of this force: a drag that limits the falling velocity and what you correctly call buoyancy. I hope this helps, Steve ———- FOLLOW-UP ———- QUESTION: Hi Steve, thanks for your response. I have another question. When an oject is free-falling through air, why is the initial air resistance acting on the object is different from the weight of the object which is acting on air?
