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ipn [44]
3 years ago
7

The concept of critical density is just like the idea of escape velocity for a projectile launched from the earth. An object lau

nched with a velocity less than the escape velocity will fall back to the earth, and an object launched with one greater than the escape velocity can escape the earth's gravitational field. Find an expression for vesc, the escape velocity of a projectile launched from the earth's surface. Express your answer in terms of the universal gravitational constant G, the mass of the earth Me, and the radius of the earth Re.
Physics
1 answer:
ikadub [295]3 years ago
5 0

Answer:

v = √ 2 G M/ R_{e}

Explanation:

To find the escape velocity we can use the concept of mechanical energy, where the initial point is the surface of the earth and the end point is at the maximum distance from the projectile to the Earth.

Initial

        Em₀ = K + U₀

Final

        Em_{f} =  U_{f}

The kinetic energy is k = ½ m v²

The gravitational potential energy is U = - G m M / r

r is the distance measured from the center of the Earth

How energy is conserved

       Em₀ =  Em_{f}

       ½ mv² - GmM / R_{e} = -GmM / r

       v² = 2 G M (1 /  R_{e} – 1 / r)

       v = √ 2GM (1 / R_{e} – 1 / r)

The escape velocity is that necessary to take the rocket to an infinite distance (r = ∞), whereby 1 /∞ = 0

        v = √ 2GM /  R_{e}

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A large flat block of mass 7 m rests on a level, smooth tabletop (µk ≈ 0). On top of it is a much smaller block of mass m, with
mariarad [96]

Answer:

3. µs g /7

Explanation:

The largest Force appear when the maximal friction Force is required.

Second Newton law for the small block:

F_friction=u_s*N=u_s*(mg)

F-F_friction=ma

F-u_s*(mg)=ma

Second Newton law for the Big Block:

F_friction=7ma

u_s*(mg)=7ma

a=u_s*g/7

8 0
3 years ago
Which of the following is NOT considered electromagnetic radiation? x-rays radio waves cosmic rays ultraviolet light
OlgaM077 [116]

Answer:

Cosmic ray is not considered electromagnetic radiation.

Explanation:

Electromagnetic radiation refers to

  • It is Radiation that has both electric and magnetic fields and travels in waves.
  • Electromagnetic radiation can vary in strength from low energy to high energy.

X rays are the rays produced when a negatively charged electrode is heated by electricity and electrons are released, thereby producing energy. It is a type of radiation called EM waves.

Radio wave are wave from the portion of the electromagnetic spectrum at lower frequencies than microwaves. It is an EM wave.

Ultraviolet wave Invisible rays that are part of the energy that comes from the sun. It is an example of EM wave.

Cosmic ray is a high-speed particle either an atomic nucleus or an electron that travels through space.

Cosmic ray is not an electromagnetic wave.

Hence

Cosmic ray is not considered electromagnetic radiation

learn more about electromagnetic radiation here:

<u>brainly.com/question/13695751</u>

#SPJ4

4 0
2 years ago
A well is pumped at Q = 300 m3 /hr in a confined aquifer. The aquifer transmissivity is 25 m2 /hr and the storage coefficient is
Effectus [21]

Answer:

(a). The draw-down at a distance 200 m from the well after pumping for 50 hr is 5.383 m.

(b). The draw-down at a distance 200 m from the well after pumping for 50 hr is 6.707 m.

Explanation:

Given that,

Energy Q=300\ m^3/hr

Transmissivity T = 25\ m^2/hr

Storage coefficient S=2.5\times10^{-4}

Distance r= 200 m

We need to calculate the draw-down at a distance 200 m from the well after pumping for 50 hr

Using formula of draw-down

s= \dfrac{Q}{4\pi T}(-0.5772-ln\dfrac{r^2S}{4tT})

Put the value into the formula

s=\dfrac{300}{4\pi\times25}(-0.5772-ln\dfrac{(200)^2\times2.5\times10^{-4}}{4\times25\times50})

s=5.383\ m

We need to calculate the draw-down at a distance 200 m from the well after pumping for 200 hr

Using formula of draw-down

s= \dfrac{Q}{4\pi T}(-0.5772-ln\dfrac{r^2S}{4tT})

Put the value into the formula

s=\dfrac{300}{4\pi\times25}(-0.5772-ln\dfrac{(200)^2\times2.5\times10^{-4}}{4\times25\times200})

s=6.707\ m

Hence, (a). The draw-down at a distance 200 m from the well after pumping for 50 hr is 5.383 m.

(b). The draw-down at a distance 200 m from the well after pumping for 200 hr is 6.707 m.

3 0
3 years ago
DesCribed briefly the method you would take in location the position of an object A defined by an ordered pair of value (8,4)
Strike441 [17]

Answer:

Explanation:

The method that I will use to locate the position of an object of ordered pair of value (8, 4) is known as the graphical method. The ordered pair of value (8, 4) is known as the coordinates. In graphical method, the coordinate will be located on the Cartesian plane having both x and y axis. The graph will be a 2-dimensional graph with y-axis being along the vertical and the x-axis along the horizontal.

The coordinates (8, 4) means that the value of x is +8 and the value of y is +4. To locate the point P(8, 4) on the graph, we will have to locate both points on the positive x and y axis respectively and then mark out their point of intersection. This point of intersection will be the position of the object defined as ordered pair of value (8,4).

3 0
3 years ago
A pendulum bob swings back and forth many times before stopping. Heat produced by _____ reduces the _____ available to the pendu
serg [7]
B. friction, energy
4 0
3 years ago
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