Chapter 19, Problem 42A

Suppose you have two life preservers that are identical in size, the first a light one filled with foam and the second a very heavy one filled with lead pellets. If you submerge these life preservers in water, upon which will the buoyant force be greater? Upon which will the buoyant force be ineffective? Why are your answers different?

To determine

To identify: The life preserver that will experience greater buoyant force. Also, the life preserver that will experience more effective buoyant force.

Explanation of Solution

Introduction:

Buoyant force:-

Pressure of water increases with depth, therefore pressure on the lower surface of an object is greater than the pressure on upper surface, it means upward force acting on lower surface of object is greater than the downward force acting on the upper surface of object hence a net force acts in upward direction which is known as buoyant force.

As the lead pallets life preserver is having higher density than water so it will sink and not affected by buoyant force and we all know density is directly proportional to the buoyant force and foam is having less density than water so its start floating and buoyant force is decreased on it .

Lead pallet life preserver is having higher density so it will sink and hence buoyant force is ineffective on it because buoyant force on an object which lie at the bottom of water is ineffective.

The sizes of foam and lead pallets preservers are same so both the preserves will displaced same amount of water when they get submerged due to which buoyant force on both of them will be equal. The foam preserver is more effective in comparison to the lead pallets preserver, because foam preserver is lighter due to which it can float.Upon lead pallets preserver buoyant force will be ineffective due to its heavy weight.

Conclusion:

The sizes of foam and lead pallets preservers are same so both the preserves will displaced same amount of water when they get submerged due to which buoyant force on both of them will be equal. The foam preserver is more effective in comparison to the lead pallets preserver, because foam preserver is lighter due to which it can float.Upon lead pallets preserver buoyant force will be ineffective due to its heavy weight.