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3 years ago

A sound wave traveling downward with a speed of about 4,000 m/s suddenly slows to 1,500 m/s not far below the Earth’s surface.

Physics

2 answers:

WINSTONCH [101]3 years ago

5 0

Speed of sound wave depends on the elasticity of medium

It is given by formula

$v = \sqrt{\frac{E}{\rho}}$

now if we are given that initially sound wave is travelling with speed 4000 m/s

Then its speed becomes 1500 m/s

so here since speed is decreased by large value

so here elasticity must decreased by large amount

A. a different kind of rock

B. an underground lake

C. an open cavity

D. a pile of dinosaur bones

So in above all options the density is changed or decreased by large value if the medium is changed to solid to liquid

So the correct answer will be

<em>B. an underground lake </em>

alexira [117]3 years ago

4 0

Answer: An underground lake

Hope that helped :D

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Which statement is true of all matter?

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Answer:

D. It must have mass and volume

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Matter include elements, molecules, humans, etc. In fact, almost every substance on Earth is considered MATTER. Therefore, the fact that a substance must "have mass and volume" is true for all matter.

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2 years ago

Select the correct answer. Which event is an example of distress (or negative stress)? A. Moving to a new city B. Getting a new

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Explanation:

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3 years ago

A block of ice(m = 14.0 kg) with an attached rope is at rest on a frictionless surface. You pull the block with a horizontal for

nadezda [96]

Answer:

a) The weight and the normal force of the block has a magnitude of 137.298 newtons and the pull force exerted on the block has a magnitude of 98 newtons.

b) The final speed of the block of ice is 9.8 meters per second.

Explanation:

a) We need to calculate the weight, normal force from the ground to the block and the pull force. By 3rd Newton's Law we know that normal force is the reaction of the weight of the block of ice on a horizontal.

The weight of the block ( $W$ ), measured in newtons, is:

$W = m\cdot g$ (1)

Where:

$m$ - Mass of the block of ice, measured in kilograms.

$g$ - Gravitational acceleration, measured in meters per square second.

If we know that $m = 14\,kg$ and $g = 9.807\,\frac{m}{s^{2}}$ , the magnitudes of the weight and normal force of the block of ice are, respectively:

$N = W = (14\,kg)\cdot \left(9.807\,\frac{m}{s^{2}} \right)$

$N = W = 137.298\,N$

And the pull force is:

$F_{pull} = 98\,N$

The weight and the normal force of the block has a magnitude of 137.298 newtons and the pull force exerted on the block has a magnitude of 98 newtons.

b) Since the block of ice is on a frictionless surface and pull force is parallel to the direction of motion and uniform in time, we can apply the Impact Theorem, which states that:

$m\cdot v_{o} +\Sigma F \cdot \Delta t = m\cdot v_{f}$ (2)

Where:

$v_{o}$ , $v_{f}$ - Initial and final speeds of the block, measured in meters per second.

$\Sigma F$ - Horizontal net force, measured in newtons.

$\Delta t$ - Impact time, measured in seconds.

Now we clear the final speed in (2):

$v_{f} = v_{o}+\frac{\Sigma F\cdot \Delta t}{m}$

If we know that $v_{o} = 0\,\frac{m}{s}$ , $m = 14\,kg$ , $\Sigma F = 98\,N$ and $\Delta t = 1.40\,s$ , then final speed of the ice block is:

$v_{f} = 0\,\frac{m}{s}+\frac{(98\,N)\cdot (1.40\,s)}{14\,kg}$

$v_{f} = 9.8\,\frac{m}{s}$

The final speed of the block of ice is 9.8 meters per second.

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2 years ago

The Force of friction between an object and the surface upon which it is sliding is 12N. The weight of the object is 20N. What i

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Answer:

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3 years ago

An electric motor rotating a workshop grinding wheel at 1.06 102 rev/min is switched off. Assume the wheel has a constant negati

kvasek [131]

Answer:

t = 106π / 30*2.1

Explanation:

$w_{i} = 1.06*10^{2}$ => 106