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3 years ago

15

The fire alarm goes off, and a 75 kg firefighter slides down a pole with a constant acceleration of a = 6 m/s square. What is th

e upward force F exerted by the pole on the firefighter? *

1 answer:

Alex17521 [72]3 years ago

3 0

Answer:

450N

Explanation:

Given data

Mass m= 75kg

Acceleration= 6m/s^2

From the Newtons first law, F=ma

substitute

F=75*6

F= 450N

Hence the force is 450N

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Which of these is an example of acceleration ?

anygoal [31]

Answer:

no picture or anything so cant anwser

Explanation:

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3 years ago

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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 $3.7\times 10^8$

4 0

3 years ago

Distanţa Buzău - Iaşi este de 72 km . Aflaţi timpul în care un autovehicul parcurge această distanţă, dacă are viteza de 72 km p

GrogVix [38]

The distance from Buzău to Iaşi is 72 km. Find out the time a vehicle travels this distance if it has a speed of 72 km per hour. Expresses the speed in the unit of measurement in SI. I give the crown! Thank you

Answer:

3600seconds

Explanation:

Given parameters:

Distance = 72km

Speed = 72km/hr

Unknown:

Time it takes for the vehicle to travel the distance = ?

Solution:

Speed is the distance divided by time;

Speed = $\frac{distance}{time}$

time = $\frac{distance}{speed }$

Insert the parameters;

time = $\frac{72}{72}$ = 1hr

The SI unit of time is in seconds;

3600 seconds is 1hr

The time is 3600seconds

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3 years ago

As the train in the image moves to the right how does the train horn sound to person a?

alina1380 [7]

Answer:

Explanation:

Person A's velocity relative to the train is 0. Therefore, the pitch of the horn will not change.

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3 years ago

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A woman is standing at the rim of a nonuniform cylindrical horizontal platform initially at rest. The platform is free to rotate

Natasha2012 [34]

Answer:

e

Explanation:

i took it myself and got it right

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3 years ago