Boat on Pond Physics question?

[kristen]

A fisherman and his young niece are in a boat on a small pond. Both are wearing life jackets. The niece is holding a large helium filled balloon by a string. Consider each action below independently and indicate whether the level of the water in the pond, Rises, Falls, is Unchanged or Cannot tell.

1. The fisherman knocks the tackle box overboard and it sinks to the bottom.
2. The niece pops the helium balloon.
3. The niece gets in the water and pops the helium balloon
4. The fisherman lowers himself in the water and floats on his back.
5. The niece finds a cup and bails some water out of the bottom of the boat
6. The fisherman lowers the anchor and it hangs one foot above the bottom of the pond.

 

[Red]

The answers are as follows:
1. The fisherman knocks the tackle box overboard and it sinks to the bottom.
The weight is the boat is reduced so the boat will rise.
2. The niece pops the helium balloon.
The helium balloon was lifting up on the boat so the boat will fall deeper into the water.
3. The niece gets in the water and pops the helium balloon.
Since the niece was holding the balloon by a string and stayed in the boat, her weight is greater than the upward force of the balloon. The boat will rise in the water.
4. The fisherman lowers himself in the water and floats on his back.
Removing the fisherman's weight from the boat will cause it to rise in the water.
5. The niece finds a cup and bails some water out of the bottom of the boat
Removing weight from the boat will cause it to rise in the water.
6. The fisherman lowers the anchor and it hangs one foot above the bottom of the pond.
Although the anchor did not touch bottom, it did displace water which reduced the amount of gravitational force it applies to the boat. The boat will rise in the water.
I hope this helps.