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padilas [110]
3 years ago
11

LASIK eye surgery uses pulses of laser light to shave off tissue from the cornea, reshaping it. A typical LASIK laser emits a 1.

0-mm-diameter laser beam with a wavelength of 193 nm. Each laser pulse lasts 15 ns and contains 1.0 mJ of light energy.(a) What is the power of one laser pulse?(b) During the very brief time of the pulse, what is the intensity of the light wave?
Physics
1 answer:
QveST [7]3 years ago
3 0

Answer:

a) 6.7 * 10⁴ W  b) 8.5* 10¹⁰ W/m²

Explanation:

a) The power of one laser pulse, by definition of power, is equal to the energy expended during the emission of the pulse, divided by the time during which the energy was present, as follows:

P = ΔE/Δt = 10⁻³ J / 15*10⁻⁹ sec = 6.7* 10⁴ W

b) The intensity, or power density, of the light wave, is just the power that we just calculated in a) divided by the cross-section area traversed by the pulse, which is a circle of 1.0 mm diameter.

So, we can write the following expression:

I = P/A = P / π*(d²/4) = 6.7*10⁴ W /( π*(10⁻³)²/4) m² = 8.5* 10¹⁰ W/m²

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a toy car moves around a loop-the-loop track.The loop is 0.5 high.What is the minimum speed of the car at the top of the loop fo
Sunny_sXe [5.5K]

Answer:

The speed of the car at the apex of the loop must be grater than 2.45 m/s

Explanation:

In order for the car to not fall off the track at the apex of the loop, the norm force of the track at the apex must be greater than zero.

Assuming frictionless life on the track which is also to have a perfectly circular shape near the top (radius being 0.25m), the norm force of the track and gravity both point down and result in the centripetal force:

F_c=F_N+F_g

The formula for centripetal force on a circular trajectory is

F_c = m\frac{v^2}{r}

and so the condition for the car to stay on the track can be written as

m\frac{v^2}{r} = F_N + mg\implies F_N = m\frac{v^2}{r}-mg>0\\\implies |v| >\sqrt{gr}=\sqrt{9.8\frac{m}{s^2}0.25m}=2.45\frac{m}{s}

The speed of the car at the apex of the loop must be grater than 2.45 m/s


3 0
3 years ago
A boy in a wheelchair (total mass 54.5 kg) has speed 1.40 m/s at the crest of a slope 2.10 m high and 12.4 m long. At the bottom
babymother [125]

Answer:

630.75 j

Explanation:

from the question we have the following

total mass (m) = 54.5 kg

initial speed (Vi) = 1.4 m/s

final speed (Vf) = 6.6 m/s

frictional force (FF) = 41 N

height of slope (h) = 2.1 m

length of slope (d) = 12.4 m

acceleration due to gravity (g) = 9.8 m/s^2

work done (wd) = ?

  • we can calculate the work done by the boy in pushing the chair using the law of law of conservation of energy

wd + mgh = (0.5 mVf^2) - (0.5 mVi^2) + (FF x  d)

wd = (0.5 mVf^2) - (0.5 mVi^2) + (FF x  d) - (mgh)

where wd = work done

m = mass

h = height

g = acceleration due to gravity

FF = frictional force

d = distance

Vf and Vi = final and initial velocity

wd =  (0.5 x 54.5 x 6.9^2) - (0.5 x 54.5 x 1.4^2) + (41 x 12.4) - (54.5 X 9.8 X 2.1)            

wd = 630.75 j

3 0
3 years ago
An atom that has fewer neutrons than protons and more electrons than protons is a ion
riadik2000 [5.3K]

i think it is an ion

6 0
3 years ago
What describes a sound wave as it travels through a medium
Softa [21]
Sound waves in air (and any fluid medium) are longitudinal waves because particles of the medium through which the sound is transported vibrate parallel to the direction that the sound wave moves.
5 0
3 years ago
Oxygen and hydrogen are kept under the same temperature and pressure. Oxygen molecule is 16 times more massive than hydrogen one
olya-2409 [2.1K]

Answer:

The average speed of molecule of oxygen is one-fourth of the speed of the hydrogen molecule.

Explanation:

The kinetic energy of gas molecule is given by following equation:

K.E = \frac{3}{2} KT

Since the temperature (T) is constant for both molecules. Therefore, there kinetic energies will also be the same. Therefore,

K.E_{O_2} = K.E_{H_2}\\\frac{1}{2}m_{O_2}v_{O_2}^2 =  \frac{1}{2}m_{H_2}v_{H_2}^2 \\\\but,\\\\m_{O_2} = 16m_{H_2}\\\\therefore,\\16 m_{H_2}v_{O_2}^2 = m_{H_2}v_{H_2}^2\\\\\\taking square root on both sides, we get:\\4v_{O_2} = v_{H_2}\\\\v_{O_2} = \frac{v_{H_2}}{4}

<u>The average speed of molecule of oxygen is one-fourth of the speed of the hydrogen molecule.</u>

7 0
3 years ago
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