Dimensional Analysis and the mathematical steps throughout a process.

In summary, the conversation discusses the relationship between time taken for an object to fall, height dropped from, mass, and acceleration due to gravity. By using dimensional analysis, it is found that time is proportional to the square root of height and the inverse square root of acceleration due to gravity, and is independent of mass. This leads to the equation t = C * square root of (h/g), where C is a constant of proportionality. The individual asking the question then asks for a detailed explanation of the mathematical steps to get from the proportional relationship to the final equation.
  • #1
Olly_price
14
0
One would assume that:

$$t \propto h^\alpha m^\beta g^\gamma$$

Where t = time taken for object to fall, h = height dropped from, m = mass, g = acceleration due to gravity.

By doing some dimensional analysis one can find that:

$$t \propto h^\frac{1}{2} g^\frac{-1}{2}$$ and that t is independant of the objects mass.

From this, one can derive that:

$$t = C \surd\frac{h}{g}$$

Where C is some unknown constant of proportionality.

MY QUESTION:

How does one get from $$t \propto h^\frac{1}{2} g^\frac{-1}{2}$$ to $$t = C \surd\frac{h}{g}$$. I need to know all the mathematical processes and each step in detail.
 
Physics news on Phys.org
  • #2
x-1/2=[itex] \sqrt{ \frac 1 x} [/itex]

How can you not know this?
 
  • #3
Integral said:
x-1/2=[itex] \sqrt{ \frac 1 x} [/itex]

How can you not know this?

Probably cos I'm 14 and haven't been taught it...
 
  • #4
Integral said:
x-1/2=[itex] \sqrt{ \frac 1 x} [/itex]

Besides, that's not even an answer to my question!

I asked for each mathematical step and all you give me is $$x^-1/2=√\frac{1}{x}$$

So come on, what's each mathematical step?
 
  • #5


To get from $$t \propto h^\frac{1}{2} g^\frac{-1}{2}$$ to $$t = C \surd\frac{h}{g}$$, we first need to understand what the symbol $\propto$ means. This symbol indicates that there is a proportional relationship between two quantities, in this case, between time (t) and the other variables (h, m, and g). In other words, as one variable changes, the other variable changes in proportion to it.

Next, we can use dimensional analysis to find the relationship between these variables. Dimensional analysis is a mathematical method used to check the validity of equations and to convert between different units of measurement. It is based on the principle that physical quantities can be expressed in terms of fundamental dimensions such as length, mass, and time.

In this case, we have four variables (t, h, m, and g) and three fundamental dimensions (length, mass, and time). This means that we can express the equation as a product of these three dimensions raised to some exponents. We can represent this as:

$$t \propto L^a M^b T^c$$

Where L represents length, M represents mass, and T represents time. The exponents a, b, and c are unknown and we need to find them.

To find the exponents, we will use the given information that t is proportional to h and g. This means that the ratio of t to h and the ratio of t to g must be constant. We can express this as:

$$\frac{t}{h} = K$$

$$\frac{t}{g} = K$$

Where K is the constant of proportionality.

Next, we can rearrange these equations to isolate t:

$$t = Kh$$

$$t = Kg$$

Now, we can substitute these values for t in our original equation:

$$Kh \propto h^\alpha m^\beta g^\gamma$$

$$Kg \propto h^\alpha m^\beta g^\gamma$$

Since the constant K is the same in both equations, we can equate the exponents of h, m, and g on both sides:

$$1 = \alpha + \beta$$

$$1 = \gamma$$

Solving for the exponents, we get:

$$\alpha = 1 - \beta$$

$$\gamma =
 

1. What is dimensional analysis?

Dimensional analysis is a method used in science to convert between different units of measurement. It involves breaking down a problem into its fundamental dimensions (such as length, mass, time) and using conversion factors to manipulate the units until the desired unit is obtained.

2. Why is dimensional analysis important in science?

Dimensional analysis is important because it allows scientists to make accurate and consistent measurements by converting between different units. It also helps in understanding the relationships between different physical quantities and in solving complex mathematical problems.

3. What are the steps involved in dimensional analysis?

The steps involved in dimensional analysis include identifying the known and unknown units, writing them in the form of a fraction, finding the appropriate conversion factors, canceling out the units, and performing the necessary mathematical operations to obtain the desired unit.

4. Can dimensional analysis be used in any scientific problem?

Yes, dimensional analysis can be used in any scientific problem where there are different units of measurement involved. It is a universal method that can be applied to a wide range of disciplines, including physics, chemistry, biology, and engineering.

5. What are some common mistakes to avoid in dimensional analysis?

Some common mistakes to avoid in dimensional analysis include using incorrect conversion factors, not canceling out units correctly, and forgetting to include all relevant units. It is also important to double-check the final unit to ensure it is the desired unit and has the correct dimensions.

Similar threads

Replies
5
Views
1K
Replies
8
Views
495
  • Other Physics Topics
Replies
2
Views
1K
  • Introductory Physics Homework Help
Replies
34
Views
673
  • Advanced Physics Homework Help
Replies
0
Views
650
Replies
3
Views
3K
Replies
20
Views
644
Replies
39
Views
2K
  • Introductory Physics Homework Help
Replies
25
Views
453
  • Other Physics Topics
Replies
19
Views
1K
Back
Top