Doing experiment to find the authenticity of Archimedes' law

[haha0p1]

Homework Statement

Describe how to use a newton-meter, a micrometer screw gauge, a metal cube of side 1 cm and a beaker of water to show experimentally that Archimedes' principle is correct. The density of water is known to be 1000kgm-³

Relevant Equations

F= pghA

I have solved the question like this:
Since Volume=Upthrust
We need to find the upthrust and the volume V. To find the volume, we will submerge the block in the water and find the difference.
To find the upthrust F, we will subtract the weight (finding the weight usinf newton-meter) from the upward force from the bottom of the block. Ergo, we will get the net upward force. Then we will compare value of Upward force F and Volume V. If the value is same, then the principle is correct.
Please tell whether this answer is right..

 

[kuruman]

Since Volume=Upthrust

Since when?

 

[haha0p1]

Since when?

Since 246 BC...Archemedes' principle suggested that the Upthrust force is equal to the volume of water displaced by the object that is submerged.

 

[BvU]

So if the volume of water displaced is 1 m³, the upthrust force is 1 N ?

 

[haha0p1]

So if the volume of water displaced is 1 m³, the upthrust force is 1 N ?

Yes, it will equal 1 N.

 

[BvU]

1. what about dimensions ?
2. No, it will not equal 1 N

 

[haha0p1]

1. what about dimensions ?
2. No, it will not equal 1 N

Kindly explain why it will not equal 1N. I can't understand it

 

[BvU]

1. Dimensions:

Upthrust is a force. Its unit is Newton. 1 Newton = 1 kg m/s².

Volume has the unit m³

The mass of a volume $V$ of water is $\rho V$ kg (rho was given to you: 1000 kg/m³).
(check the dimensions: kg/m³ times m³ is kg).

The weight of a volume $V$ of water is $\rho V g$ N ($g$ is 9.81 m/s²)
(check the dimensions: kg/m³ times m³ times m/s² is kg m/s²).

2. Now, can you

explain why it will not equal 1N.

?

 

[BvU]

Since 246 BC...Archimedes' principle ... Upthrust force is equal to the volume ...

Check that, e.g. here !

$\$

 

[haha0p1]

Check that, e.g. here !

$\$

Ohkok Now I got it. I was incorrect as I said that Upthrust is equal to the volume of water displaced. It was actually the weight of the water that was displaced!

 

[kuruman]

Ohkok Now I got it. I was incorrect as I said that Upthrust is equal to the volume of water displaced. It was actually the weight of the water that was displaced!

Yup.

 

[Steve4Physics]

Homework Statement:: Describe how to use a newton-meter, a micrometer screw gauge, a metal cube of side 1 cm and a beaker of water to show experimentally that Archimedes' principle is correct. The density of water is known to be 1000kgm-³
Relevant Equations:: F= pghA

I have solved the question like this:
Since Volume=Upthrust
We need to find the upthrust and the volume V. To find the volume, we will submerge the block in the water and find the difference.

The scale on the side of a beaker is not very accurate, especially for measuring small volume-changes. Why do you think a micrometer screw gauge is supplied?

To find the upthrust F, we will subtract the weight (finding the weight usinf newton-meter) from the upward force from the bottom of the block.

EDIT: The upwards force is the upthrust. It is unclear what you actually do to find it.

Ergo, we will get the net upward force.

It helps to define symbols for different quantities - then you can give a formula.

Then we will compare value of Upward force F and Volume V. If the value is same, then the principle is correct.

That's wrong. See previous posts. You will need explain how to find the weight of water displaced.

General point: a good way to answer this sort of question is to give numbered steps. Each step is written as an instruction to someone, telling them exactly/clearly what they need to do.

 

[kuruman]

That's wrong. See previous posts. You will need explain how to find the weight of water displaced.

In addition to that, if the purpose of the experiment is to verify Archimedes's principle as the title suggests, then you need to determine the "upthrust" independently and compare the two numbers. If they are equal to within experimental error, then the principle has been verified.

Providing a step-by-step experimental procedure as @Steve4Physics suggested is an excellent start. It will help us diagnose any problems in what you propose to do and the finished product will be your guide when you actually perform the experiment.

 

[Lnewqban]

For more precise values of pure water density, consider its temperature for the experiment:
https://en.wikipedia.org/wiki/Density#Water