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3 years ago

A person standing for a long time gets tired when he does not appear to do any work .why?

Physics

1 answer:

Keith_Richards [23]3 years ago

6 0

Explanation:

A person standing still for a long time feels tired because the force of gravity acts on our body and puts stress on our muscles. so our muscles need energy to do work and keep body balanced and help to stand upright.

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Into molecules of sugar and oxygen.
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4 years ago

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3 years ago

Four electrons are located at the corners of a square 10.0 nm on a side, with an alpha particle at its midpoint. How much work i

Elis [28]

Four electrons are placed at the corner of a square

So we will first find the electrostatic potential at the center of the square

So here it is given as

$V = 4\frac{kQ}{r}$

here

r = distance of corner of the square from it center

$r = \frac{a}{\sqrt2}$

$r = \frac{10nm}{\sqrt2} = 7.07 nm$

$Q = e = -1.6 * 10^{-19} C$

now the net potential is given as

$V = \frac{4 * 9*10^9 * (-1.6 * 10^{-19})}{7.07 * 10^{-9}}$

$V = 0.815 V$

now potential energy of alpha particle at this position

$U_i = qV = 2*1.6 * 10^{-19} * (-0.815) = -2.6 * 10^{-19} J$

Now at the mid point of one of the side

Electrostatic potential is given as

$V = 2\frac{kQ}{r_1} + 2\frac{kQ}{r_2}$

here we know that

$r_1 = \frac{a}{2} = 5 nm$

$r_2 = \sqrt{(a/2)^2 + a^2} = \frac{\sqrt5 a}{2}$

$r_2 = 11.2 nm$

now potential is given as

$V = 2\frac{9 * 10^9 * (-1.6 * 10^{-19})}{5 * 10^{-9}} + 2\frac{9*10^9 * (-1.6 * 10^{-19})}{11.2 * 10^{-9}}$

$V = -0.576 - 0.257 = -0.833 V$

now final potential energy is given as

$U_f = q*V = 2*1.6 * 10^{-19}* (-0.833) = -2.67 * 10^{-19} J$

Now work done in this process is given as

$W = U_f - U_i$

$W = (-0.267 * 10^{-19}) - (-0.26 * 10^{-19}}$

$W = -7 * 10^{-22} J$

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3 years ago

A soccer player icks a rock horizontally off a 40m high cliff into a pool f water if the player hears the sound of the splash s

Semenov [28]

Answer:

v = 9.936 m/s

Explanation:

given,

height of cliff = 40 m

speed of sound = 343 m/s

assuming that time to reach the sound to the player = 3 s

now,

time taken to fall of ball

$t = \sqrt{\dfrac{2s}{g}}$

$t = \sqrt{\dfrac{2\times 40}{9.8}}$

t = 2.857 s

distance

d = v x t

d = v x 2.875

time traveled by the sound before reaching the player

$t_0 = t - t_{fall}$

$t_0 = 3 - 2.875$

$t_0 = 0.143 s$

distance traveled by the wave in this time'

r = 0.143 x 343

r= 49.05 m

now,

we know.

d² + h² = r²

d² + 40² = 49.05²

d =28.387 m

v x 2.875=28.387 m

v = 9.936 m/s

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3 years ago

A tennis ball machine serves a ball vertically into the air from a height of 2 feet, with an initial speed of 130 feet per secon

Maurinko [17]

<span>Од сила е еднаква на масата * aceleration Ние го имаме тоа сила = 5N, маса = 0.6kg a =? 5 = 0,6 * a. Затоа a = 5 / 0,6 a = 8.33m / s² Ве молиме да се одбележи мене како brainliest.</span>

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3 years ago

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A person standing for a long time gets tired when he does not appear to do any work .why?​

A person standing for a long time gets tired when he does not appear to do any work .why?