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lukranit [14]
3 years ago
8

In order to walk barefoot on hot coals without hurting your feet

Physics
1 answer:
siniylev [52]3 years ago
5 0

Before a person walks through burning coal, the person will make sure their feet are very wet. When they start walking on the coal, this moisture will evaporate and form a protective gas layer underneath the person's feet. You can see examples of this if you happen to drip some water on a hot stove or any very hot surface. The water will very easily glide around on top of a newly formed layer of air underneath it -- like air hockey pucks on an air hockey table. Note that when someone walks through burning coal, typically this is also done very quickly to prevent a great deal of exposure to possible harm. By walking quickly, thinking positively, and letting the water cushion you from immediate danger over a short distance, such a task is possible. You may have also heard of physics teachers demonstrating how this principle works by sticking their hand first in a bucket of water and then quickly in a bucket of boiling molten lead. In the lead, their hand is protected briefly by a layer of gas from the evaporated water (the water vapor). I'm fairly sure that there is a name for this particular layer of gas, but I'm afraid the name is beyond me at the moment. In other words, water vapor has a low heat capacity and poor thermal conduction. Very often, the coals or wood embers that are used in fire walking also have a low heat capacity. Sweat produced on the bottom of people's feet also helps form a protective water vapor. All of this together makes it possible, if moving quickly enough, to walk across hot coals without getting burned. WARNING: Do not attempt to perform any of the actions described above. You can seriously injure yourself. Answered by: Ted Pavlic, Electrical Engineering Undergrad Student, Ohio St.  (citing my source)

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At a distance of 11 cm from a presumably isotropic, radioactive source, a pair of students measure 65 cps (cps = counts per seco
Alborosie

To solve the problem, it is necessary the concepts related to the definition of area in a sphere, and the proportionality of the counts per second between the two distances.

The area with a certain radius and the number of counts per second is proportional to another with a greater or lesser radius, in other words,

A_1*m=M*A_2

A_i =Area

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Our radios are given by

r_1 = 11cm

R_2 = 20cm

m = 65cps

Therefore replacing we have that,

A_1*m=M*A_2

4\pi r_1^2*m = M * 4\pi R_2^2 M

r^2*m=MR^2

M = \frac{m*r^2}{R^2}

M = \frac{65*11^2}{20^2}

M = 19.6625cps

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7 0
3 years ago
Proved that<br>V = u+at<br>​
kondaur [170]

Answer:

\sf Proof \ below

Explanation:

We know that acceleration is change in velocity over time.

\sf a=\frac{\triangle v}{t}

\sf a=\frac{v-u}{t}

v is the final velocity and u is the initial velocity.

Solve for v.

Multiply both sides by t.

\sf at=v-u

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3 0
3 years ago
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A uniform electric field of magnitude 7.0 ✕ 104 N/C passes through the plane of a square sheet with sides 5.0 m long. Calculate
Vadim26 [7]

Answer:

1.52*10^6 Nm^2/C

Explanation:

Given that:

Electrical field E = 7.0 * 10^{-4}N/C

square side l = 5.0 m

Area A = 5.0 * 5.0

= 25.0 m²

Angle ( θ ) between area vector and E = (90° - 60°)

= 30°

The flux \phi_E can now be determined by using the expression

\phi_E = E*A*Cos \theta

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\phi_E = 1515544.457 Nm^2/C

\phi_E = 1.52*10^6 Nm^2/C

5 0
3 years ago
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Please I need help on this one kinda lost on it
Vanyuwa [196]
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