A man is sitting in a boat which is floating in a pond. If the man drinks some water from the pond, the level of the water in the pond decreases.
Answer: False
Or read the worked solution below. Jump to the steps ↓
Written solution
Step 1: Analyze the initial equilibrium of the floating boat.
For a floating boat of mass containing a man of mass , the buoyant force equals the total weight of the system.
The initial volume of water displaced by the boat, , is:
Step 2: Express the initial water level of the pond.
Let be the volume of the water in the pond, and be the horizontal cross-sectional area of the pond. The initial water level is given by:
Step 3: Determine the changes after the man drinks water.
When the man drinks a mass of water from the pond, two changes occur:
- The volume of the liquid water in the pond decreases:
- The total mass of the boat-man system increases by , which increases the displaced volume:
Step 4: Calculate the new water level.
Substitute the new values into the expression for the new water level .
The change in water level is:
The water level remains unchanged.
Answer: The given statement is False (the level of the water in the pond remains the same).