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anzhelika [568]

2 years ago

9

Spot welding is used to fuse two sheets of metal together at one small spot. Two copper electrodes pinch the sheets together at

a point and then run a huge electric current through that point. The two sheets melt and flow together to form a spot weld. Why does this technique work only with relatively poor conductors of electricity such as stainless steel and not with excellent conductors such as copper?

1 answer:

hjlf2 years ago

7 0

Answer:

The power deposited in a metal is proportional to its electric resistance, so high-resistance metals heat more.

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What is the speed of an object at rest

Alisiya [41]

The speed of an object at rest is 0 m/s. We can use logic to figure this out. Hope this helps!

8 0

2 years ago

A rocket ship leaves Earth's atmosphere. Its initial velocity is less than its final velocity. What is this an example of?

77julia77 [94]

I believe this would be an example of positive acceleration as the initial velocity of the rocket is less than the final velocity, indicating that the rocket is accelerating and thus is positive.

6 0

2 years ago

Read 2 more answers

7) Sound waves travel with a nominal speed of 340 m/s. Calculate the wavelengths of the following musical notes:

Oksana_A [137]

The wavelength for C1 note is 10.40 m, for A6 note is 0.193 m and for B7 note 0.086 m.

Answer:

Explanation:

Since, wavelength, frequency and speed of sound waves are related to each other, we can determine a single parameter with the help of other two parameters. So in this case, the frequency of different notes are given along with their common speed. So as the frequency is inversely proportional to the wavelength then in this case, the wavelength of the notes will be maximum for C1 and minimum for 3951.1 Hz.

Wavelength = Speed / Frequency

Wavelength for C1 note = 340 / 32.7 =10.40 m

Similarly, the wavelength for A6 note = 340/1760=0.193 m

And, the wavelength for B7 note = 340/3951.1 = 0.086 m

So, the wavelength for C1 note is 10.40 m, for A6 note is 0.193 m and for B7 note 0.086 m.

6 0

3 years ago

A cylinder with a piston contains 0.200 mol of oxygen at 2.00×105 Pa and 360 K . The oxygen may be treated as an ideal gas. The

ikadub [295]

Answer:

A. $W=600\ J$

B. $Q=2112\ J$

C. $\Delta U=1512\ J$

D. $W=0\ J$

Explanation:

Given:

no. of moles of oxygen in the cylinder, $n=0.2$

initial pressure in the cylinder, $P_i=2\times 10^5\ Pa$

initial temperature of the gas in the cylinder, $T_i=360\ K$

<em>According to the question the final volume becomes twice of the initial volume.</em>

<u>Using ideal gas law:</u>

$P.V=n.R.T$

$2\times 10^5\times V_i=0.2\times 8.314\times 360$

$V_i=0.003\ m^3$

A.

<u>Work done by the gas during the initial isobaric expansion:</u>

$W=P.dV$

$W=P_i\times (V_f-V_i)$

$W=2\times 10^5\times (0.006-0.003)$

$W=600\ J$

C.

<u>we have the specific heat capacity of oxygen at constant pressure as:</u>

$c_v=21\ J.mol^{-1}.K^{-1}$

Now we apply Charles Law:

$\frac{V_i}{T_i} =\frac{V_f}{T_f}$

$\frac{0.003}{360} =\frac{0.006}{T_f}$

$T_f=720\ K$

<u>Now change in internal energy:</u>

$\Delta U=n.c_p.(T_f-T_i)$

$\Delta U=0.2\times 21\times (720-360)$

$\Delta U=1512\ J$

B.

<u>Now heat added to the system:</u>

$Q=W+\Delta U$

$Q=600+1512$

$Q=2112\ J$

D.

Since during final cooling the process is isochoric (i.e. the volume does not changes). So,

$W=0\ J$

7 0

2 years ago

a mass stands on a platform which vibrates simple harmonically in a vertical Direction and with a frequency of 5 Hertz. show tha

Nastasia [14]

shm

displacement is A*sin 2pi f t

vel =( A*2*pi*f*)*cos 2 pi f t

accn =-( A*2*pi*f*)^2*sin 2 pi f t

accn = (0.01*2*3*5)

accn = (0.01x30)^2=9

4 0

3 years ago