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3 years ago

Sound is a mechanical wave; therefore, it __________.

2 answers:

8 0

A mechanical wave such as sound needs a medium to travel through. This is why they say that in space, no one can hear you scream (because space is a vacuum and no medium exists). On the contrary, light can exist in wave or particle form. This is why we have the ability to see beyond the realms of the Earth.

miss Akunina [59]3 years ago

6 0

Answer:

The answer is A. Must travel trought a medium.

Explanation:

The transmission of sound depends on the existence of a material medium (solid, liquid, air particles) where the vibration of the molecules are perceived as a sound wave, which are converted into mechanical waves in the human ear, to be later perceived by the brain.

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How does the work required to accelerate a particle from 10 m/s to 20 m/s compare to that required to accelerate it from 20 m/s

poizon [28]

To solve this problem we will apply the energy conservation theorem for which the work applied on a body must be equivalent to the kinetic energy of this (or vice versa) therefore

$W = \Delta KE$

$\Delta W = \frac{1}{2} (m)(v_f)^2 -\frac{1}{2} (m)(v_i)^2$

Here,

m = mass

$v_{f,i}$ = Velocity (Final and initial)

First case) When the particle goes from 10m/s to 20m/s

$\Delta W = \frac{1}{2} (m)(v_f)^2 -\frac{1}{2} (m)(v_i)^2$

$\Delta W = \frac{1}{2} (m)(20)^2 -\frac{1}{2} (m)(10)^2$

$W_1 = 150(m) J$

Second case) When the particle goes from 20m/s to 30m/s

$\Delta W = \frac{1}{2} (m)(v_f)^2 -\frac{1}{2} (m)(v_i)^2$

$\Delta W = \frac{1}{2} (m)(30)^2 -\frac{1}{2} (m)(20)^2$

$W_1 = 250(m) J$

As the mass of the particle is the same, we conclude that more energy is required in the second case than in the first, therefore the correct answer is A.

5 0

3 years ago

a stone is dropped from the top of 50 m high tower simultaneously another stone is thrown upward with a speed of 20 m/s . calcul

Darina [25.2K]

'H' = height at any time
'T' = time after both actions
'G' = acceleration of gravity
'S' = speed at the beginning of time
Let's call 'up' the positive direction.
Let's assume that the tossed stone is tossed from the ground, not from the tower.

For the stone dropped from the 50m tower:

H = +50 - (1/2) G T²

For the stone tossed upward from the ground:

H = +20T - (1/2) G T²

When the stones' paths cross, their Heights are equal.

50 - (1/2) G T² = 20T - (1/2) G T²

Wow ! Look at that ! Add (1/2) G T² to each side of that equation,
and all we have left is:

50 = 20T Isn't that incredible ? ! ?

Divide each side by 20 :

2.5 = T

The stones meet in the air 2.5 seconds after the drop/toss.

I want to see something:
What is their height, and what is the tossed stone doing, when they meet ?

Their height is +50 - (1/2) G T² = 19.375 meters

The speed of the tossed stone is +20 - (1/2) G T = +7.75 m/s ... still moving up.
I wanted to see whether the tossed stone had reached the peak of the toss,
and was falling when the dropped stone overtook it. The answer is no ... the
dropped stone was still moving up at 7.75 m/s when it met the dropped one.

7 0

3 years ago

A ball is thrown vertically upward with a speed of 1.86

Inessa05 [86]

Answer:

t = 1.09 s.

Explanation:

This is a one-dimensional kinematics question, so the equations of kinematics will be sufficient to solve the question.

$y-y_0 = v_0t + \frac{1}{2}at^2\\0 - 3.82 = 1.86t +\frac{1}{2}(-9.8)t^2\\-3.82 = 1.86t - \frac{1}{2}9.8t^2\\4.9t^2 - 1.86t - 3.82 = 0$

This quadratic equation can be solved using determinant.

$\Delta = b^2 - 4ac\\t_{1,2} = \frac{-b \pm \sqrt{\Delta} }{2a}\\t_1 = 1.09~s\\t_2 = -0.71~s$

Of course, we will choose the positive time.

4 0

3 years ago

Find a glass jar with a screw-top metal lid. Close the lid snugly and put the jar into the refrigerator. Leave it there for abou

DochEvi [55]

Answer:

The lid becomes tighter

It becomes tighter because metals have a lower heat capacity than glass meaning their temperature drops (or increases) much faster than glass for the same energy change. So in this example, the metal will contract faster than the glass causing it to be more tighter around the glass.

5 0

3 years ago

What is a measurement of the earths history divided into time periods?

Pie

Fossil Record

Geologic Time Scale

3 0

2 years ago

Read 2 more answers