Deformation of Solids: Solving Question 18 from 9702_s13_qp_13

In summary, the conversation is about a student seeking help on a physics question from a past paper. The specific question is about the model and full size counterparts of a cable and how they compare in terms of force, area, and length. The proper approach to solving the question involves considering the proportional relationships between force, weight, volume, area, and length in relation to the linear dimension of the model and full size counterparts.
  • #1
yan_plusheartz
7
0

Homework Statement



Hey, I have problems solving this question. May I know how to solve this question. Somehow, the answer I got is to the power of negative. can someone show me the step by step solution to this question? (Question 18 from this paper) the link is below.
http://maxpapers.com/wp-content/uploads/2012/11/9702_s13_qp_13.pdf


Homework Equations


E = Fl / Ae


The Attempt at a Solution

 
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  • #2
Hello Yan, and welcome to PF. There's a few rules here that are universally accepted -- and severely imposed.
One is to use the template. You did that in a smart way. Laziness can be a good quality in physics.
But you missed number 1 and number 3. The first error could have been avoided by rendering the problem instead of dumping the whole exam. The other is unforgivable, since it prevents helpers from helping you properly.

At first I thought I might help you a little by alleviating the stress that can accompany having to struggle at an exam. but the date tells me this is practicing. So we have the time, right? Let's use it effectively, both yours and that of potential helpers.

This is what I found at number 18 on a first attempt:

18 The formula for hydrostatic pressure is p = ρ gh.
Which equation, or principle of physics, is used in the derivation of this formula?
A density =mass/volume
B potential energy = mgh
C atmospheric pressure decreases with height
D density increases with depth
 
  • #3
yan_plusheartz said:

Homework Statement



Hey, I have problems solving this question. May I know how to solve this question. Somehow, the answer I got is to the power of negative. can someone show me the step by step solution to this question? (Question 18 from this paper) the link is below.
http://maxpapers.com/wp-content/uploads/2012/11/9702_s13_qp_13.pdf


Homework Equations


E = Fl / Ae


The Attempt at a Solution

I think you are thinking of question 19, correct?

How do the weights of the masses compare to their full size counterparts?
How does the cross sectional area of the cable compare to its full size counterpart?
How do the lengths of the cables compare to their full size counterparts?
 
  • #4
Oops my mistake, it's question 19 actually.

It is stated that linear dimension of the model is 1/10 of the full size

So e is directly proportional to Fl/A since E is the same for both
Hence e model = (1/10)F x (1/ 10) l / (1/10) A
e full size = F l /A
e model : e full = 10^-1
However, the right answer is 10^2
May I know what is the proper approach to this? Thx
 
  • #5
yan_plusheartz said:
Oops my mistake, it's question 19 actually.

It is stated that linear dimension of the model is 1/10 of the full size

So e is directly proportional to Fl/A since E is the same for both
Hence e model = (1/10)F x (1/ 10) l / (1/10) A
e full size = F l /A
e model : e full = 10^-1
However, the right answer is 10^2
May I know what is the proper approach to this? Thx
The force is equal to the weight of the mass. The weight of the mass is proportional to its volume. Volume is proportional to its linear dimension cubed cubed. The area of the cable is proportional to its linear dimension squared. The length of the cable is proportional to its linear dimension to the first power.
 
  • #6
ImageUploadedByPhysics Forums1392296383.288636.jpg


Okay, now that you have explained this to me , I kinda have a rough idea about the question. So here's my working:) is it correct?
However, I can't really relate the last proportionality you explained just now to me . In my working, I just times 1/10 to the force (load) , length and also volume. Is it the right way?
 
  • #7
yan_plusheartz said:
View attachment 66581

Okay, now that you have explained this to me , I kinda have a rough idea about the question. So here's my working:) is it correct?
However, I can't really relate the last proportionality you explained just now to me . In my working, I just times 1/10 to the force (load) , length and also volume. Is it the right way?
No. 1/1000 the force, 1/100 the area, and 1/10 the length.
 
  • #8
Okay. Here's my new working. Is it correct ?
ImageUploadedByPhysics Forums1392300235.893834.jpg
 
  • #9

1. What is deformation of solids?

Deformation of solids is the change in shape, size, or volume of a solid material due to an applied force or stress. This can result in either temporary or permanent changes to the material's physical properties.

2. What are the different types of deformation?

The three main types of deformation are elastic, plastic, and fracture. Elastic deformation is reversible and the material returns to its original shape when the force is removed. Plastic deformation is irreversible and causes a permanent change in the material's shape. Fracture occurs when the applied force exceeds the material's strength, causing it to break or crack.

3. What factors affect the deformation of solids?

The deformation of solids is affected by the material's properties, such as elasticity and strength, as well as the type of force applied and the duration of the force. Temperature and pressure can also play a role in the deformation of solids.

4. How is deformation of solids measured?

Deformation of solids can be measured using various techniques such as strain gauges, extensometers, or by analyzing changes in the material's dimensions. These measurements can provide information about the material's strength, elasticity, and stress-strain relationship.

5. What are the practical applications of studying deformation of solids?

Understanding deformation of solids is important in fields such as engineering, materials science, and geology. It can help in designing and testing structures, predicting and preventing failures, and understanding the behavior of materials under different conditions. It also has applications in manufacturing processes and product development.

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