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3 years ago

How many photons strike the cd surface during the playing of a cd 69 minutes in length?

Physics

1 answer:

Reptile [31]3 years ago

8 0

Answer:

Photons strike the CD $n=1.624 x10^{18}$

Explanation:

First of all, it is necessary to calculate the energy produced by a semiconductor laser for 69 minutes:

$69minutes*\frac{60s}{1 minute}=4140s$

$E=0.1x10^{-3}w*4140s=0.414J$

Next, it is possible to calculate the number of photons striking the CD surface during this time:

$E=\frac{n*h*c}{l}$

$l=780x10^{-9}m$ long in CD

$c=3x10^8 m/s$ light velocity

$h=6.626x10^{-34} J*s$

Solve to n'

$n=\frac{E*l}{c*h}=\frac{0.414 J*780x10^{-9}m}{3x10^8m/s*6.626x10^{-34}}$

$n=1.624 x10^{18}$

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In a playground, there is a small merry-go-round of radius 1.20 m and mass 160 kg. Its radius of gyration is 91.0 cm. (Radius of

aksik [14]

Answer:

a) 145.6kgm^2

b) 158.4kg-m^2/s

c) 0.76rads/s

Explanation:

Complete qestion: a) the rotational inertia of the merry-go-round about its axis of rotation

(b) the magnitude of the angular momentum of the child, while running, about the axis of rotation of the merry-go-round and

a) From I = MK^2

I = (160Kg)(0.91m)^2

I = 145.6kgm^2

b) The magnitude of the angular momentum is given by:

L= r × p The raduis and momentum are perpendicular.

L = r × mc

L = (1.20m)(44.0kg)(3.0m/s)

L = 158.4kg-m^2/s

c) The total moment of inertia comprises of the merry- go - round and the child. the angular speed is given by:

L = Iw

158.4kgm^2/s = [145kgm^2 + ( 44.0kg)(1.20)^2]

w = 158.6/208.96

w = 0.76rad/s

7 0

3 years ago

What happens when you want to move the boat forward? You pull the oars toward yourself.Explain why you do this.

vampirchik [111]

Answer:

You pull on the oars. By the third law, the oars push back on your hands, but that’s irrelevant to the motion of the boat. The other end of each oar (the blade) pushes against the water. By the third law, the water pushes back on the oars, pushing the boat forward.

8 0

3 years ago

Read 2 more answers

A circular loop of flexible iron wire has an initial circumference of 165cm , but its circumference is decreasing at a constant

ArbitrLikvidat [17]

Answer:

emf induced is 0.005445 V and direction is clockwise because we can see area is decrease and so that flux also decrease so using right hand rule direction of current here clockwise

Explanation:

Given data

initial circumference = 165 cm

rate = 12.0 cm/s

magnitude = 0.500 T

tome = 9 sec

to find out

emf induced and direction

solution

we know emf in loop is - d∅/dt ........1

here ∅ = ( BAcosθ)

so we say angle is zero degree and magnetic filed is uniform here so that

emf = - d ( BAcos0) /dt

emf = - B dA /dt ..............2

so area will be

dA/dt = d(πr²) / dt

dA/dt = 2πr dr/dt

we know 2πr = c,

r = c/2π = 165 / 2π

r = 26.27 cm

c is circumference so from equation 2

emf = - B 2πr dr/dt ................3

and

here we find rate of change of radius that is

dr/dt = 12/2π = 1.91 $10^{-2}$ cm/s

so when 9.0s have passed that radius of coil = 26.27 - 191 (9)

radius = 9.08 $10^{-2}$ cm

so now from equation 3 we find emf

emf = - (0.500 ) 2π(9.08 $10^{-2}$ ) 1.91 $10^{-2}$

emf = - 0.005445

and magnitude of emf = 0.005445 V

emf induced is 0.005445 V and direction is clockwise because we can see area is decrease and so that flux also decrease so using right hand rule direction of current here clockwise

4 0

3 years ago

how much heat is required to raise the temperature 500 of song of iron from 50°to 250°c? (take c=480j/kg°c)

Mars2501 [29]

Answer:

Explanation:

523 degrees

5 0

3 years ago

What is a neoplasm? A. Another word for a malignant tumor B. A type of carcinoma that grows only in the mouth C. A benign swelli

Umnica [9.8K]

<h2>Answer: Any new and abnormal growth</h2>

A <u>neoplasm</u> is any <u>uncontrolled growth</u> of abnormal cells or tissues in the body.

This abnormal mass can be benign or malignant (carcinogenic).

Therefore, the correct option is D.

3 0

3 years ago