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2 years ago

8

Ultraviolet rays from the sun are able to reach Earth's surface because A. They require air to travel through B. They have less

energy than infrared rays C. They have lower frequencies than visible light D. They can travel through empty space

1 answer:

9966 [12]2 years ago

3 0

Yeah, because of it's short frequencies, ultraviolet rays can travel through empty space- D
: D

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You attach a 3.10 kg weight to a horizontal spring that is fixed at one end. You pull the weight until the spring is stretched b

dolphi86 [110]

Answer:

0.785 m/s

Explanation:

Hi!

To solve this problem we will use the equation of motion of the harmonic oscillator, <em>i.e.</em>

$x(t) = A cos(\omega t )+B sin(\omega t)$ - (1)

$\frac{dx}{dt}(t) = \omega (B cos(\omega t )- A sin(\omega t)$ - (1)

The problem say us that the spring is released from rest when the spring is stretched by 0.100 m, this condition is given as:

$x(0) = 0.100$

$\frac{dx}{dt}(0) = 0$

Since cos(0)=1 and sin(0) = 0:

$x(0)=A$

$\frac{dx}{dt}(0) = -B\omega$

We get

$A =0.100\\B = 0$

Now it say that after 0.4s the weigth reaches zero speed. This will happen when the sping shrinks by 0.100. This condition is written as:

$x(0.4) = - 0.100$

Since

$x(t) = 0.100 cos(\omega t)\\ -0.100=x(0.4)=0.100cos(\omega 0.4)$

This is the same as:

$-1 = cos(0.4\omega)$

We know that cosine equals to -1 when its argument is equal to:

(2n+1)π

With n an integer

The first time should happen when n=0

Therefore:

π = 0.4ω

or

ω = π/0.4 -- (2)

Now, the maximum speed will be reached when the potential energy is zero, <em>i.e. </em>when the sping is not stretched, that is when x = 0

With this info we will know at what time it happens:

$0 = x(t) = 0.100cos(\omega t)$

The first time that the cosine is equal to zero is when its argument is equal to π/2

<em>i.e.</em>

$t_{maxV}=\pi /(2\omega)$

And the velocity at that time is:

$\frac{dx}{dt}(t_{maxV} ) =- 0.100\omega sin(\omega t_{maxV})\\\frac{dx}{dt}(t_{maxV} ) =- 0.100\omega sin(\pi/2)\\$

But sin(π/2) = 1.

Therefore, using eq(2):

$\frac{dx}{dt}(t_{maxV} ) = 0.100*\omega = 0.100\frac{\pi}{0.400} = \pi/4$

And so:

$V_{max} = \pi / 4 =0.785$

6 0

2 years ago

Công thức dùng tính tần số dao động của con lắc lò xò

tino4ka555 [31]

Answer:

f = 1 / [ 2*pi*R*C*Sqrt(2*N)

Explanation:

f = 1 / [ 2*pi*R*C*Sqrt(2*N) is the formula. Sorry I answered in English.

6 0

3 years ago

When a football is kicked, the action and reaction forces do NOT cancel each other out because

AfilCa [17]

Answer:

C

Explanation:

The kicker exerts more force of the football which is why the football moves when its kicked.

6 0

3 years ago

Calculate the pressure of water in a will if the deep of the water is 10 m

Bas_tet [7]

Answer:

98,000 pa

Explanation:

The formula for water pressure is as follows:

$pressure = pgh$

Where <em>p </em>is the density of water (in kg/m3), <em>g </em>is the gravitational field strength, and <em>h </em>is the height of the water.

The density of water is 1000kg/m3, the gravitational field strength is 9.8, and the height is 10. Substituting in these values:

$pressure = 1000 \times 9.8 \times 10$

$pressure = 98000$

7 0

2 years ago

As the ambulance got closer, Marge noticed that the pitch of the siren got higher. This happened because

AfilCa [17]

A) the sound waves were pushed closer together

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3 years ago

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