Force vs Weight: Which is Heavier?

In summary, the weight registered on the scale will be the same whether the flies are sitting on the bottom of the jar or flying around inside, as the mass of the jar (including the flies) remains constant. This is due to the force exerted by the air on the jar, which is transmitted to the scale regardless of the location of the flies. The only way the weight would change is if the flies were performing some kind of collective motion.
  • #1
havechanged
21
0
Hey!

Okay, there are a bunch of flies in a capped jar. You place the jar on a scale. The scale will register the most weight when the flies are:

A. sitting on the bottom of the jar.

B. flying around inside the jar.

C. weight of the jar is the same in both cases.


I can't organize my thoughts! I can't explain this.

Any help will be greatly appreciated!
 
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  • #2
C.

The flies are suspended in air, the air forces down on the jar. That's assuming the flies are not performing some collective motion. For example, if they all suddenly dive to the bottom, the jar will be momentarily lighter, regaining normal weight when they land.
 
  • #3
Yeah, that is what I was thinking...it is just driving me crazy because I can't collect my thoughts as to the "scientific" reason this is so. Hmm...thanks though!
 
  • #4
Well, for a scientific reason, think about this. The mass of the jar (which includes the flies inside of it) does not change depending on the location of the flies. Unless they perform some act like krab said.
 
  • #5
Agreed. The answer, without special circumstances, is C.
 
  • #6
Originally posted by havechanged
Hey!

Okay, there are a bunch of flies in a capped jar. You place the jar on a scale. The scale will register the most weight when the flies are:

A. sitting on the bottom of the jar.

B. flying around inside the jar.

C. weight of the jar is the same in both cases.


I can't organize my thoughts! I can't explain this.

Any help will be greatly appreciated!

First, if you consider the MASS "jar+flies", that is definately a constant whatever the flies are doing: sitting or flying.

Now, if you consider the weight of the "jar+flies", that means you are looking at force that is exerced on the scale. There is there tree contribution to that force: from the jar (constant force), from the air in the jar and from the flies in the jar. Now do not forget that the flies rely on the air to be able to fly. Therefore, whether they sit on the bottom or they fly should not make any difference. In the air, the wings of the a fly exert on average a force on the air which is transmitted to the bottom of the jar and therefore to the scale. If there was no air (vaccum), the fly could simply not fly and would always rest at the bottom.

An easier picture would be to consider the jar filled with water whith a fish swiming in the jar. It would not matter if the fish float at the surface, sit a the bottom or swim in the middle: the fish weight applies a force on the water which is transmitted to the bottom of the jar.

Note: you may find that the force is not always constant in time and that the force is fluctuating during the measurement. That is because when the fish/flies move around they exert additional forces necessary to accelerate/decelerate their motions. However, these fluctuation should average to zero and the average weight in time should be "jar+air/water+flies/fish". Think that it is the same when you try to measure your own weight on a scale but you do not stay still...
 
  • #7
If the flies are all accelerating upwards, the jar will register the highest value.
 
  • #8
Originally posted by FZ+
If the flies are all accelerating upwards, the jar will register the highest value.

And if they are accelerating downwords - stooping ?
 

1. What is the difference between force and weight?

Force is a measure of the push or pull on an object, while weight is a measure of the force of gravity on an object. Force is a vector quantity, meaning it has both magnitude and direction, while weight is a scalar quantity, only having magnitude.

2. Which one is heavier, force or weight?

Neither force nor weight can be considered "heavier" as they are two different physical quantities. However, weight is often used to describe the perceived heaviness of an object due to the force of gravity acting on it.

3. How are force and weight related?

Weight is directly proportional to force. This means that as the force acting on an object increases, so does its weight. Weight is also affected by the acceleration due to gravity, which varies depending on the location.

4. Can an object have a greater force than its weight?

Yes, an object can have a greater force than its weight. This can happen when the object is accelerating, as the force of acceleration adds to the force of gravity, making the total force greater than the weight of the object.

5. How do we measure force and weight?

Force is typically measured in Newtons (N), while weight is measured in Newtons (N) or pounds (lbs). Force can be measured using a spring scale or force meter, while weight can be measured using a scale or by using the formula W = mg, where W is weight, m is mass, and g is the acceleration due to gravity.

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