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3 years ago

Compared to arc welding, which of the following statements are true about gas welding?

Engineering

1 answer:

UNO [17]3 years ago

4 0

Show than arc welding

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Block D of the mechanism is confined to move within the slot of member CB. Link AD is rotating at a constant rate of ωAD = 6 rad

svet-max [94.6K]

Answer:

1) 1.71 rad/s

2) -6.22 rad/s²

Explanation:

Choose point C to be the origin.

Using geometry, we can show that the coordinates of point A are:

(a cos 30°, a sin 30° − b)

Therefore, the coordinates of point D at time t are:

(a cos 30° − b sin(ωt), a sin 30° − b + b cos(ωt))

The angle formed by CB with the x-axis is therefore:

tan θ = (a sin 30° − b + b cos(ωt)) / (a cos 30° − b sin(ωt))

1) Taking the derivative with respect to time, we can find the angular velocity:

sec² θ dθ/dt = [(a cos 30° − b sin(ωt)) (-bω sin(ωt)) − (a sin 30° − b + b cos(ωt)) (-bω cos(ωt))] / (a cos 30° − b sin(ωt))²

sec² θ dθ/dt = -bω [(a cos 30° − b sin(ωt)) sin(ωt) − (a sin 30° − b + b cos(ωt)) cos(ωt)] / (a cos 30° − b sin(ωt))²

sec² θ dθ/dt = -bω [(a cos 30° sin(ωt) − b sin²(ωt)) − (a sin 30° cos(ωt) − b + b cos²(ωt))] / (a cos 30° − b sin(ωt))²

sec² θ dθ/dt = -bω (a cos 30° sin(ωt) − b sin²(ωt) − a sin 30° cos(ωt) + b − b cos²(ωt)) / (a cos 30° − b sin(ωt))²

sec² θ dθ/dt = -bω (a cos 30° sin(ωt) − a sin 30° cos(ωt)) / (a cos 30° − b sin(ωt))²

sec² θ dθ/dt = -abω (cos 30° sin(ωt) − sin 30° cos(ωt)) / (a cos 30° − b sin(ωt))²

We know at the moment shown, a = 350 mm, b = 200 mm, θ = 30°, ω = 6 rad/s, and t = 0 s.

sec² 30° dθ/dt = -(350) (200) (6) (cos 30° sin(0) − sin 30° cos(0)) / (350 cos 30° − 200 sin(0))²

sec² 30° dθ/dt = -(350) (200) (6) (-sin 30°) / (350 cos 30°)²

dθ/dt = (200) (6) (1/2) / 350

dθ/dt = 600 / 350

dθ/dt = 1.71 rad/s

2) Taking the second derivative of θ with respect to time, we can find the angular acceleration.

sec² θ d²θ/dt² + 2 sec² θ tan θ dθ/dt = -abω [(a cos 30° − b sin(ωt))² (ω cos 30° cos(ωt) + ω sin 30° sin(ωt)) − (cos 30° sin(ωt) − sin 30° cos(ωt)) (2 (a cos 30° − b sin(ωt)) (-bω cos(ωt)))] / (a cos 30° − b sin(ωt))⁴

At t = 0:

sec² θ d²θ/dt² + 2 sec² θ tan θ dθ/dt = -abω [(a cos 30°)² (ω cos 30°) − (0 − sin 30°) (2 (a cos 30°) (-bω))] / (a cos 30°)⁴

sec² θ d²θ/dt² + 2 sec² θ tan θ dθ/dt = -abω (a²ω cos³ 30° − 2abω sin 30° cos 30°) / (a⁴ cos⁴ 30°)

sec² θ d²θ/dt² + 2 sec² θ tan θ dθ/dt = -bω (aω cos² 30° − 2bω sin 30°) / (a² cos³ 30°)

d²θ/dt² + 2 tan θ dθ/dt = -bω² (a cos² 30° − b) / (a² cos 30°)

Plugging in values:

d²θ/dt² + 2 tan 30° dθ/dt = -(200) (6)² (350 cos² 30° − 200) / (350² cos 30°)

d²θ/dt² + 2 tan 30° dθ/dt = -7200 (262.5 − 200) / (350² cos 30°)

d²θ/dt² + 2 tan 30° (1.71) = -4.24

d²θ/dt² = -6.22 rad/s²

4 0

2 years ago

Your manager has asked you to research and recommend a writing guide that examiners in your digital forensics company can use fo

vivado [14]

Answer:

Kindly Check the explanation

Explanation:

Report

A Report is a way to present the forensic examination result in front of judge. A report contains warrants, all affidavits issued for arrest, expenses occur during forensic test and lists of evidence. Apart from evidence a report also contains expert opinions.

Guidelines

These are the set of rules and written statement which are used to present the important information in a structured and clear format. The main motive behind to define the guidelines is to achieve standardization in the reports. It also improves the readability of the report.

Guidelines for report

Abstract:

Each report must contain an abstract of the report which gives the brief review about the report. It came at the starting of the report. The main motive behind to give abstract is to give brief about report to someone in a very less time. The size of abstract must not be more than one page.

Index:

Each report must contain an index which display's which content is available at which page of report. The content of index must be appropriate and clear so that the reader will not get confuse.

Format of report:

The formatting of report is also one of the essential parts of the guidelines. It makes the report attractive and also due to this reader not gets bored while reading the report. The guidelines regarding layout of report are as follow:

1. Use time roman font and 12 font size as a default font to explain anything in the report.

2. The explanation must be justified

3. As possible divide the long paragraph. if possible explain in points.

4. The page must have border on all sides

5. Each pages must have numbering and footer

Rules for grammar:

1. The language of the report must be simple and clear. So that everyone can understand it easily.

2. Avoid repeating same sentence or word again and again.

3. Use active instead of passive voice, in order to give importance to doer.

4. Write expressions between commas.

5. Avoid spelling mistakes in report which also make wrong impact.

6. As possible give heading or subheading to material or explanation which must be accurate.

7. Explain, new or difficult words used in the report.

8. What ever written in the report must be through the point and accurate on bases of fact.

Body of report:

The body of the report referred to as a content written inside the report. In order to write an impressive report, it must include all these things:

1. Avoid use of hypothetical question, if still hypothetical question arises it must be bases on factual evidence.

2. Add all the affidavits and warrants in the report issued for search and arrest.

3. The cost money expenses while solving the case.

4. The expert opinion which must be bases on knowledge or previously declare case results.

5. The list of people and evidence which are collected and interrogative during the investigation.

6. If investigation is further going on than write the area in which the investigation further goes on and also mention when the investigation get complete.

Forensic software used:

A short must be given about the software used in the investigation. The result generated by the software must also be pasted in that report. It is more good if attach the snap shot of the result. Add any previous case result in which the same software result is taken as evidence, in order to justify that the result generated by the software is true. Some of forensic softwares are FTK, ProDiscover, Hexworkshop. The result of these softwares must be heighted so that everyone can notice it.

Conclusion:

The conclusion must be given at the end of report to tell according him what result came after investigation. In conclusion also write on which basis the result concludes. There must be strong behind the conclusion.

References:

In Reference write all the cases, thesis, books which an investigator followed to solve the current case. In addition if they referred any internet article. They can also write the website name where that article lies. In short can say that write everything where they got an idea which is helpful in solving the case.

8 0

3 years ago

Very thin films are usually deposited under vacuum conditions to prevent contamination and ensure that atoms can fly directly fr

katrin [286]

Answer:

a. 9947 m

b. 99476 times

c. 2*10^11 molecules

Explanation:

a) To find the mean free path of the air molecules you use the following formula:

$\lambda=\frac{RT}{\sqrt{2}\pi d^2N_AP}$

R: ideal gas constant = 8.3144 Pam^3/mol K

P: pressure = 1.5*10^{-6} Pa

T: temperature = 300K

N_A: Avogadros' constant = 2.022*10^{23}molecules/mol

d: diameter of the particle = 0.25nm=0.25*10^-9m

By replacing all these values you obtain:

$\lambda=\frac{(8.3144 Pa m^3/mol K)(300K)}{\sqrt{2}\pi (0.25*10^{-9}m)^2(6.02*10^{23})(1.5*10^{-6}Pa)}=9947.62m$

b) If we assume that the molecule, at the average, is at the center of the chamber, the times the molecule will collide is:

$n_{collision}=\frac{9947.62m}{0.05m}\approx198952\ times$

c) By using the equation of the ideal gases you obtain:

$PV=NRT\\\\N=\frac{PV}{RT}=\frac{(1.5*10^{-6}Pa)(\frac{4}{3}\pi(0.05m)^3)}{(8.3144Pa\ m^3/mol\ K)(300K)}=3.14*10^{-13}mol\\\\n=(3.14*10^{-13})(6.02*10^{23})\ molecules\approx2*10^{11}\ molecules$