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VladimirAG [237]
3 years ago
7

In a perfect vacuum, light waves travel at 300,000 kilometers every second. When light waves travel through materials, such as a

ir, they
A.speed up

B.slow down

C.increase in amplitude

D.Heat up
Physics
2 answers:
ruslelena [56]3 years ago
3 0
They slow down so the answer is B
yanalaym [24]3 years ago
3 0

c = speed of light in vacuum = 300,000 kilometers/second

n = index of refraction of material

v = speed of light in the material

Speed of light in a given material is given as

v = C/n

v = 300,000/n

for air, the value of index of refraction "n" is slightly greater, hence the speed of light in air is smaller than 300,000 kilometers/second. hence the light waves slow down.

so correct choice is

B.slow down

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A 62.0 kg sprinter starts a race with an acceleration of 1.44 m/s2. If the sprinter accelerates at that rate for 30 m, and then
Dominik [7]

Answer:

The time taken for the race is 17.20 s.

Explanation:

It is given in the problem that a 62.0 kg sprinter starts a race with an acceleration of 1.44 meter per second square.The initial speed of the sprinter is zero as it starts from the rest.

Calculate the final speed of the sprinter.

The expression for the equation of the motion is as follows;

v^{2}-u^{2}= 2as

Here, u is the initial speed, v is the final speed, a is the acceleration and s is the distance.

Put u= 0, s=30 m and a= 1.44 ms^{-2}.

v^{2}-(0)^{2}= 2(1.44)(30)

v= 9.3 m^{-1}

Calculate time taken to cover 30 m distance.

The expression for the equation of motion is as follows;

s=ut+\frac{(1)}{2}at^2

Put u= 0, s=30 m and a= 1.44 ms^{-2}.

30=(0)t+\frac{(1)}{2}(1.44)t^2

t=6.45 s

Calculate the time taken to complete his race.

T= t+t'

Here, t is the time taken to cover 30 m distance and t' is the time taken to cover 100 m distance.

T=6.45+\frac{s'}{v}

Put s= 30 m, v= 9.3 m^{-1} and s'= 100 m.

T=6.45+\frac{(100)}{9.3}

T= 17.20 s

Therefore, the time taken for the race is 17.20 s.

6 0
3 years ago
ASAP answer all pls will mark brainiest
sammy [17]

Answer:

1) B

2)D

Explanation:

I am unsure of #2

7 0
2 years ago
Read 2 more answers
What is the magnitude of the force, directed parallel to the ramp, that he needs to exert on the crate to get it to start moving
lions [1.4K]

Complete question is;

Jason works for a moving company. A 75 kg wooden crate is sitting on the wooden ramp of his truck; the ramp is angled at 11°.

What is the magnitude of the force, directed parallel to the ramp, that he needs to exert on the crate to get it to start moving UP the ramp?

Answer:

F = 501.5 N

Explanation:

We are given;

Mass of wooden crate; m = 75 kg

Angle of ramp; θ = 11°

Now, for the wooden crate to slide upwards, it means that the force of friction would be acting in an opposite to the slide along the inclined plane. Thus, the force will be given by;

F = mgsin θ + μmg cos θ

From online values, coefficient of friction between wooden surfaces is μ = 0.5

Thus;

F = (75 × 9.81 × sin 11) + (0.5 × 75 × 9.81 × cos 11)

F = 501.5 N

3 0
3 years ago
Làm thế mào để kiểm tra một lục ma sát trược
9966 [12]
C I completed the same quiz
4 0
2 years ago
Suppose astronomers built a 150-meter telescope. how much greater would its light-collecting area be than that of the 10-meter k
Dennis_Churaev [7]
Almost all telescopes have a circular mirror. The area of a circle is proportional to r^2 where r is the radius of the circle, the constant of proportionality being 4\pi
S =4\pi r^2
Therefore the area of 150 meter telescope would be 
S_1/S_2=(r_1/r_2)^2 =(75/5)^2 =15^2=225
times bigger than the area of the smaller (10 meter) telescope.

6 0
2 years ago
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