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3 years ago

7

500 J of work are done in 4 seconds to lift a 40 kg box to the top of a high shelf. How much power was required to complete the

lift?

1 answer:

Artemon [7]3 years ago

5 0

Answer:

125 W

Explanation:

Power = work / time

P = 500 J / 4 s

P = 125 W

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Which events took place during the Copernican revolution, when most people started to believe in a heliocentric model of the sol

balu736 [363]

<h2>2) Copernicus rediscovered Aristarchus’s heliocentric model.</h2>

Before Copernican Revolution, people did believe in the ptolemain model that establishes the description of the Universe with the earth at the center having sun, moon, starts and planets all orbited earth. On the other hand, the heliocentric model establishes the sun at the center of the solar system and this starts with the publication of Nicolas Copernicus named <em>De revolutionibus orbium coelestium.</em>

<h2>5) Newton’s theories of gravity increased understanding of the movement of planets.</h2>

The revolution ended with Isaac Newton's work over a century later. As you well know, Newton was both a physicist and mathematician, better known for his prodigal work called <em>Philosophiæ Naturalis Principia Mathematica. </em>In this revolution, he is known for his laws of motion and universal gravitation increasing understanding of the movement of planets.

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3 years ago

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An aquarium open at the top has 30-cm-deep water in it. You shine a laser pointer into the top opening so it is incident on the

Setler [38]

Answer:

You must add 8cm of water to the tank

Explanation:

In order to find how much the height is we will use the Snell Refraction law

.

This law relates the index of refraction of the water (n2), the index of refraction of the air (n1), the incidence angle relative to the vertical (theta1) and the refraction angle relative to the vertical (theta2) by using the next equation:

$(n1)*(sin(theta1))=(n2)*(sin(theta2))$

Then we will find the refraction angle relative to the vertical this way:

$(n1/n2)*(sin(theta1))=sin(theta2)$

$(1/1.33)*(sin(45))=sin(theta2)$

Then, theta2=32.12°

Now that we have this information we can imagine a triangle with a 30cm height and a 32.12° angle. This way we can find how much X is, this X will be the distance between the vertical line and the spot the beam hits the bottom, so we can use some trigonometry to find it, this way:

$tan(32.12)=(X/30cm)$

$X=(tan(32.12))*(30cm)$

Then, X=18.8cm, we can approximate it to 19cm

Once we have X we will add 5cm to it which is how much the beam needs to be moved, then the new X will be 24cm

Now, with the new horizontal distance we will find the new vertical distance, let´s call it Y, this way we will know how much water we must add to move the beam, then we will have a triangle with a vertical distance called Y, the same 32.12° angle will be used as we are still working with the air-water interface and a 19cm horizontal distance, then:

$tan(32.12)=(24cm/Y)$

$Y=(24cm/tan(32.12))$

Then, Y=38cm

In this case, you must add 8cm of water to the tank to move the beam on the bottom 5cm

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3 years ago

Which of these help create radio waves?

Margaret [11]

The correct option is A.
All waves are divided into two basic classes, which are transverse and longitudinal waves. A transverse wave is a type of wave in which the medium of propagation vibrates at angle 90 degree in relation to the direction of propagation. Radio wave is an example of a transverse wave.

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3 years ago

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The total mechanical energy of a system is 950 J and the gravitational potential energy is 350 J. What is the kinetic energy?

romanna [79]

Answer:

<em>The kinetic energy is 600 J</em>

Explanation:

<u>Mechanical Energy</u>

The principle of the conservation of mechanical energy states that the total mechanical energy in a system remains constant as long as the only forces acting are conservative forces.

The mechanical energy is defined as the sum of the potential plus kinetic energies:

E = U + K

Where E is the total mechanical energy, U is the gravitational potential energy and K is the kinetic energy.

Solving for K:

K = E - U

The system described has a total mechanical energy of E=950 J and gravitational potential energy of U=350 J, thus:

K = 950 J - 350 J

K = 600 J

The kinetic energy is 600 J

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3 years ago

At 7:00 pm the police discovered a body in a hotel room which maintained a constant temperature of 24 degree C. At the time of d

schepotkina [342]

Explanation:

According to Newton's law of cooling,

$T(t)=T_s+(T_o-T_s){e^{{-t/\tau}}$

T(t) is the temperature at time t

$T_s$ is temperature of surrounding

$k=\dfrac{1}{\tau}$

At the time of discovery, the temperature of the dead body was, $T_o=36^{\circ}C$

Temperature of the surrounding, $T_s=24^{\circ}C$

Temperature after 4 hours, $T=30^{\circ}C$

So, $30=24+(36-24)e^{-4t}$

On solving the above equation,

k = 0.1735

Now, put the value of k in equation (1) at T = 36 degrees C

We know that, the temperature of body before death is T(t) = 37 degrees C

$37=24+(36-24)e^{0.17t}$

On solving above equation,

t = -0.46 hour

As time can't be negative and we have taken 7:00 pm as reference time.

So, t = 27.67 minutes

So, the death of the person is at 6 : 32 pm. Hence, this is the required solution.

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3 years ago