Btt-19 Obidjonov Jahongir

Read this:

A survey was made of the weights of 74 vehicles passing over a bridge. The results of the survey were recorded as follows:

Weight in tonnes	Number of vehicles
0 to ^1/4	1
^1/4 to ^1/2	3
^1/2 to ^3/4	7
^3/4 to 1	15
1 to 1 ^1/4	20
1 ^1/4 to 1 ^1/2	13
1 ^3/4 to ^3/4	8
l^3/4 to 2	4
2 to 2 %	2
2^1/4 to 2^1/2	1

Copy the diagram at the top of page 111 and use the results to make a bar chart.



Now complete these sentences predicting average future loads from vehicles on the bridge:

1. 
   It is impossible that the load will be less than 0 tonnes.
   
2. 
   The likelihood that the load will be 0-3 tonnes is low.
   
3. 
   It is improbable that the load will exceed 2 tonnes.
   
4. 
   The most frequent load on the bridge will probably be between _3/4 and 1 ¹/2 tonnes.
   

7. Now read this:

74 identical structural components were tested for tensile strength. The results were as follows:

Tensile strength at failure in tonnes	Number of components
1 ^1/4 to 1^1/2	4
1^1/2 to P/4	18
1^1/4 to 2	30
2 to 2^1/4	18
2^1/4 to 2 ^1/2	4

Copy the diagram in exercise 9 again and use these results to make another bar chart.

Now say whether these statements are true or false. Correct the false statements.

1. 
   Most of the components failed at a load between 1 ¹/2 and 1³/4 tonnes. FALSE (Most of the components failed at a load between 1³/4 and 2 tonnes)
   
2. 
   No components failed below a load of 1¹/4 tonnes. TRUE
   
3. 
   Nearly all the components failed above a load of 1 ^l/2 tonnes. TRUE
   
4. 
   Very few components failed over a load of 2¹/2 tonnes. FALSE (No components failed over a load of 2¹/2 tonnes)
   
5. 
   If these components are used in a bridge which is loaded to destruction, they will probably fail at a load between 2 and 2¹/4 tonnes. FALSE (If these components are used in a bridge which is loaded to destruction, they will probably fail at a load between 2³/4 and 2tonnes)
   

11 Read this:

There is great uncertainty about the magnitude of the loads that will occur on this bridge. However, there is more certainty about the magnitude of the strength of the bridge, i.e. its ability to resist the loads, because it is a simple structure. The graph of probability against load and strength for the bridge will

look like this:

Probability
, _t _ design load safety factor Jesign
strength

Now match these two graphs with these two design situations. Say when there is great certainty or uncertainty about loads or strength:

Water tower in Great Britain
Graph A
Design situation 1


Multi-storey building ng ^rain^phJa^Bpan
Design situation 2 J'J\ Load Strength

Probability
Probability

In which situation will the safety factor be 2 and in which 6?

Section 4 Listening

9. Look at the pairs of drawings on page 113 and discuss them:

Each pair of drawings shows a design mistake which could be dangerous, and a way of reducing the danger.

13. Now listen to the passage and list the numbers of the diagrams in the order you hear them described.

(I can't answer this question since I don't have audio lessons)

13. 
    Listen to the passage again and for each pair of diagrams take notes on:
    

1. 
   the design mistake
   
2. 
   the possible event resulting from the mistake
   
3. 
   the action needed to correct the design mistake Now use these notes to make paragraphs like this:
   

External fire escapes can become wet and icy. As a result, people may slip and injure themselves when escaping from a fire. Therefore, if it is possible, a fire escape should be enclosed and protected from the weather.