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3 years ago

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A person jumps from the roof of a house 3.1-m high. When he strikes the ground below, he bends his knees so that his torso decel

erates over an approximate distance of 0.70 m. If the mass of his torso (excluding legs) is 42kg .
Part A
Find his velocity just before his feet strike the ground.
Express your answer using two significant figures. Enter positive value if the velocity is upward and negative value if the velocity is downward.

1 answer:

Sveta_85 [38]3 years ago

3 0

Part A

Free fall motion
h = 3.1 m

Equation: Vf = √(2gh) = √(2*9.8 m/s^2 * 3.1 m) = 7.8 m/s

That is the only part in the question.

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A diffraction pattern forms when light passes through a single slit. The wavelength of the light is 691 nm. Determine the angle

expeople1 [14]

Explanation:

Given that,

Wavelength of the light, $\lambda=691\ nm=691\times 10^{-9}\ m$

(a) Slit width, $a=3.8\times 10^{-4}\ m$

The angle that locates the first dark fringe is given by :

$sin\theta=\dfrac{\lambda}{a}$

$sin\theta=\dfrac{691\times 10^{-9}}{3.8\times 10^{-4}}$

$\theta=0.104^{\circ}$

(b) Slit width, $a=3.8\times 10^{-6}\ m$

The angle that locates the first dark fringe is given by :

$sin\theta=\dfrac{\lambda}{a}$

$sin\theta=\dfrac{691\times 10^{-9}}{3.8\times 10^{-6}}$

$\theta=10.47^{\circ}$

Hence, this is the required solution.

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3 years ago

A microwave oven operating at 1.22 × 108 nm is used to heat 165 mL of water (roughly the volume of a teacup) from 23.0°C to 100.

ANTONII [103]

<u>Answer:</u> The number of photons are $3.7\times 10^8$

<u>Explanation:</u>

We are given:

Wavelength of microwave = $1.22\times 10^8nm=0.122m$ (Conversion factor: $1m=10^9nm$ )

To calculate the energy of one photon, we use Planck's equation, which is:

$E=\frac{hc}{\lambda}$

where,

h = Planck's constant = $6.625\times 10^{-34}J.s$

c = speed of light = $3\times 10^8m/s$

$\lambda$ = wavelength = 0.122 m

Putting values in above equation, we get:

$E=\frac{6.625\times 10^{-34}J.s\times 3\times 10^8m/s}{0.122m}\\\\E=1.63\times 10^{-24}J$

Now, calculating the energy of the photon with 88.3 % efficiency, we get:

$E=1.63\times 10^{-24}\times \frac{88.3}{100}=1.44\times 10^{-24}J$

To calculate the mass of water, we use the equation:

$Density=\frac{Mass}{Volume}$

Density of water = 1 g/mL

Volume of water = 165 mL

Putting values in above equation, we get:

$1g/mL=\frac{\text{Mass of water}}{165mL}\\\\\text{Mass of water}=165g$

To calculate the amount of energy of photons to raise the temperature from 23°C to 100°C, we use the equation:

$q=mc\Delta T$

where,

m = mass of water = 165 g

c = specific heat capacity of water = 4.184 J/g.°C

$\Delta T$ = change in temperature = $T_2-T_1=100^oC-23^oC=77^oC$

Putting values in above equation, we get:

$q=165g\times 4.184J/g.^oC\times 77^oC\\\\q=53157.72J$

This energy is the amount of energy for 'n' number of photons.

To calculate the number of photons, we divide the total energy by energy of one photon, we get:

$n=\frac{q}{E}$

q = 53127.72 J

E = $1.44\times 10^{-24}J$

Putting values in above equation, we get:

$n=\frac{53157.72J}{1.44\times 10^{-24}J}=3.7\times 10^{28}$

Hence, the number of photons are $3.7\times 10^8$

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3 years ago

Who is Isaac Newton?<br><br>Take the points, Im leaving Brainly..

icang [17]

Answer: English

. mathematician

. physicist

. astronomer

. theologian

. author

Explanation:

Take the points, Im leaving Brainly.. Why?!

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3 years ago

The electroscope is an apparatus used to detect electric charge. The electroscope consists of a plate, a support and a free to r

Marat540 [252]

Answer:

Positive

Explanation:

The leaves will diverge further: The positive charge on the leaves has increased further. This occurs when positive charge is produced on the leaves by the charged object. This is quite possible only when the object is positively charged.

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3 years ago

Help me pls, class starts soon

ratelena [41]

Answer:

Explanation:

1.)66.36

2.)11.4

3.)0.8104

4.)4158.315

i got some of them and try the rest good luck

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3 years ago