Calculating the Mass of a Steel Wrench in Water: A Density Dilemma

  • Thread starter bww
  • Start date
  • Tags
    Water
In summary, the conversation discusses how a steel wrench feels 3N lighter in water and how to calculate the mass of the wrench based on this information. It is mentioned that the buoyancy force felt on an object is equal to the weight of the fluid it displaces. However, to calculate the mass of the wrench, the density of the steel is also needed. The conversation ends with the suggestion to look up the density of steel in a book.
  • #1
bww
17
0
A steel wrench feels 3N lighter in water.

a. what is the mass of the wrench?
b. how would your answer change if it took a more dense fluid to make the wrench feel 3N lighter?

a. ok so i know that density x volume=mass. The density of water is 1,000kg/m^3. That's about all I have. I don't really know where to go when i only have the weight of the steel and the density of water.

What are your thoughts?
 
Physics news on Phys.org
  • #2
The bouyancy force felt upwards on an object is equal to the weight of the fluid it displaces.

- Warren
 
  • #3
...i guess I'm still confused.
 
  • #4
You know how much the displaced water weighs (it's given), and you know water's density, so you can calculate the volume of water that was displaced. The volume of displaced water is, of course, is the same as the wrench's volume.

You also know the density of the steel, so you're all set to find the wrench's mass.

- Warren
 
  • #5
how do i know the density of steel?
 
  • #6
You said you know "the weight of the steel," by which I thought you mean density.

- Warren
 
  • #7
oh, no, I'm terribly sorry, my mistake. I meant that all i knew was that the weight of the wrench was 3N lighter in water. I do not have the density of the wrench. I only know that it weighs 3N less in water and that water's density is 1,000kg/m^3 and I need to find the mass of the wrench. sorry about that.
 
  • #8
Well, I don't think there's any way to do this without another piece of information (like the density of steel).

Buoyancy isn't concerned with mass, just volume. If the wrench feels a buoyancy force of 3N, then you know its volume directly. But, as you know, you cannot relate mass and volume without knowing density.

The fact that the problem specifies that the wrench is made of steel leads me to believe you are supposed to look up the density of steel. It's probably given in a table in your book somewhere. Look up 'density' in the index.

- Warren
 
  • #9
...yeah you're right, you guys are a lot of help here. thanks. i figured it out.
 
  • #10
I have the same question
 

1. How do you calculate the mass of a steel wrench in water?

To calculate the mass of a steel wrench in water, you will need to know the density of the steel wrench and the density of water. First, measure the volume of the steel wrench by either submerging it in water and measuring the displaced water, or by using a ruler to measure its dimensions. Then, multiply the volume by the density of steel to find the mass of the wrench. Next, submerge the wrench in water and measure the volume of water displaced. Finally, multiply the volume of water displaced by the density of water to find the mass of the water. The difference between the two masses is the mass of the steel wrench in water.

2. What is the purpose of calculating the mass of a steel wrench in water?

The purpose of calculating the mass of a steel wrench in water is to determine its buoyancy. Knowing the buoyancy of an object is important for understanding its behavior in water, such as whether it will float or sink. This information is also useful for engineering and design purposes.

3. What is the density of steel?

The density of steel can vary depending on the type and grade of steel. However, on average, the density of steel is around 7.8 g/cm³. This means that for every cubic centimeter of steel, there is 7.8 grams of mass.

4. How does the density of the steel wrench affect its buoyancy in water?

The density of the steel wrench plays a significant role in its buoyancy in water. If the density of the steel wrench is greater than the density of water, it will sink. However, if the density of the steel wrench is less than the density of water, it will float.

5. Can the mass of a steel wrench in water be negative?

No, the mass of a steel wrench in water cannot be negative. Mass is a physical property that represents the amount of matter in an object. It cannot have a negative value. If the calculated mass of a steel wrench in water is negative, it is likely due to a calculation error or incorrect data.

Similar threads

  • Introductory Physics Homework Help
Replies
2
Views
949
  • Introductory Physics Homework Help
Replies
17
Views
1K
  • Introductory Physics Homework Help
Replies
24
Views
2K
  • Introductory Physics Homework Help
Replies
4
Views
2K
  • Introductory Physics Homework Help
Replies
9
Views
1K
  • Introductory Physics Homework Help
Replies
11
Views
1K
  • Introductory Physics Homework Help
Replies
26
Views
795
  • Introductory Physics Homework Help
Replies
13
Views
577
  • Introductory Physics Homework Help
Replies
7
Views
2K
  • Introductory Physics Homework Help
Replies
7
Views
1K
Back
Top