If a 2-kg ball is thrown through the air at 20 m/s what is the momentum of the ball?

What is the current in a wire of radius R = 2.02 mm if the magnitude of the current density is given by (a) Ja = J0r/R and (b) J

Sloan [31]

Explanation:

For this problem we have to take into account the expression

J = I/area = I/(π*r^(2))

By taking I we have

I = π*r^(2)*J

(a)

For Ja = J0r/R the current is not constant in the wire. Hence

$I(r) = \pi r^{2} J(r) = \pi r^{2} J_{0}r/R = \pi r^{3} (3.74*10^{4}A/m^{2})/(2.02*10^{-3}m)$

and on the surface the current is

$I(R) = \pi r^{2} J(R) = \pi r^{2} J_{0}R/R = \pi(2.02*10^{-3})^{2} (3.74*10^{4}) = 0.47 A$

(b)

For Jb = J0(1 - r/R)

$I(r)=\pi r^{2}J(r) =\pi r^{2} J_{0}(1 - r/R)=\pi r^{2}J_{0}(1-\frac{r}{2.02*10^{-3}} )$

and on the surface

$I(R)=\pi r^{2}J_{0}(1-R/R)=\pi r^{2}J_{0}(1-1)= 0$

(c)

Ja maximizes the current density near the wire's surface

Additional point

The total current in the wire is obtained by integrating

$I_{T}=\pi\int\limits^R_0 {r^{2}Ja(r)} \, dr = \pi \frac{J_{0}}{R}\int\limits^R_0 {r^{3}} \ dr =\pi \frac{J_{0}R^{4}}{4R}=\frac{1}{4}\pi J_{0}R^{3}=2.42*10^{-4} A$

and in a simmilar way for Jb

$I_{T}=\pi J_{0} \int\limits^R_0 {r^{2}(1-r/R)} \, dr = \pi J_{0}[\frac{R^{3}}{3}-\frac{R^{2}}{2R}]=\pi J_{0}[\frac{R^{3}}{3}-\frac{R^{2}}{2}]$

And it is only necessary to replace J0 and R.

I hope this is useful for you

regards

7 0

3 years ago

The waste product of photosynthesis is:

zalisa [80]

Answer:

The waste product of photosynthesis is oxygen

6 0

3 years ago

A 6.25 L tank holds helium gas at a pressure of 1759 psi. A second 6.25 L tank holds oxygen at a pressure of 467.7 psi. The two

rodikova [14]

Answer:

P=1113.35 psi

Explanation:

For tank 1

V₁= 6.25 L

P₁=1759 psi

For tank 2

V₂=6.25 L

P₂=467.7 psi

Lets take final pressure is P

The final volume V= 6.25 + 6.25 L = 12.5 L

P V = V₂P₂+V₁P₁

Now by putting the values

P V = V₂P₂+V₁P₁

P x 12.5 = 6.25 x 467.7+6.25 x 1759

P=1113.35 psi

So the final volume of the system will be 1113.35 psi.

8 0

3 years ago

What should he do next in order to follow the steps of inquiry?

andrezito [222]

Since he wonders, then according to the formal, methodical procedures of scientific inquiry, he should not go running off and trying stuff before he <em>forms a hypothesis that can be tested.</em>

In his mind, at some point, he should say to himself <em>"Self ! It seems to me that if salt is added to water, it makes the water boil at a higher temperature than pure water does."</em>

And only THEN, with this statement in mind, he's ready to design an experiment to test it.

6 0

3 years ago

When compared to strong nuclear force gravitational force is

pickupchik [31]

Answer is A
Gravitational force is substantially weaker than the strong nuclear force.

6 0

4 years ago

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