Does placing something in water affect the water's weight?

In summary, the discussion revolves around a fire truck carrying firefighters and a large tank of water that may be too heavy for a bridge to support. The chief suggests that some firefighters get into the tank to reduce the weight of the system. The group debates whether this would actually make a difference, considering the principle that rearranging components of a system does not change its mass. However, it is acknowledged that the buoyant force of the water in the tank may balance out the weight of the firefighter, leading to a potential decrease in the overall weight of the system.
  • #1
Dmitri10
19
0
"A fire truck carrying a load of fire fighters and a large tank of water is about to cross a bridge that may not support the load. The chief suggests that some of the fire fighters get into the tank so the load will be less. Is this a good idea? Explain."

I have no idea where to begin. I know that the fire fighters will displace a volume of water equal to their own, but I don't know if that would change the weight of the whole system. Any help or leads would be appreciated.
 
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  • #2
The weight of the system depends on the total mass of the system. By placing firefighters in the tank, does its mass change?
 
  • #3
Does the mass of something change when you rearrange its components? If you move a book from the side pocket of your backpack to the main pocket, is the backpack going to get lighter/heavier?
 
  • #4
No... the mass of the system doesn't change. That's what I initially thought, but then I proceeded to confuse myself by trying to reason that if something were suspended in a liquid, the liquid exerts an upward buoyant force that balances out the downward force of gravity. If the downward force of gravity (the weight) of one of the objects is being balanced out, won't the weight of the system change?
 
  • #5
When the firefighter was sitting on his seat, his weight was balanced out by the normal force of the seat. If he goes into the tank, it'll be balanced out by buoyancy.
 
  • #6
Your logic is sound. Thanks for the help!
 

1. How does placing something in water affect the water's weight?

When placing an object in water, the water's weight will increase by the weight of the object. This is because the object displaces a certain amount of water, and this displaced water adds to the overall weight of the water.

2. Does the weight of the object also affect the water's weight?

Yes, the weight of the object does have an impact on the water's weight. The heavier the object, the more water it will displace, resulting in a larger increase in the water's weight.

3. Is there a limit to how much weight an object can add to the water?

No, there is no limit to how much weight an object can add to the water. As long as the object is able to displace water, it will continue to add to the water's weight.

4. Does the shape or size of the object affect the water's weight?

Yes, the shape and size of the object do have an impact on the water's weight. Objects with a larger surface area will displace more water, resulting in a greater increase in the water's weight.

5. Can placing multiple objects in water affect the water's weight differently?

Yes, placing multiple objects in water can affect the water's weight differently. This is because each object will displace a certain amount of water, and the total weight of the water will be the sum of all the displaced water from each object.

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