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3 years ago

Does the earths magnetic field change with time?

Physics

1 answer:

ZanzabumX [31]3 years ago

6 0

Answer:

As per the fossil fuel records, magnetic field reversal does not impact living beings. It will take almost a century for the poles to complete the shift. Meanwhile, the earth is left with almost zero magnetic field.

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One of the most efficient engines built so far has the following characteristics: combustion chamber temperature = 1900°C, exhau

suter [353]

Answer:

actual efficiency is 47.78 %

Carnot efficiency is 67.65 %

power output is 5.20 × 10^3 hp

Explanation:

given data

temperature = 1900°C = 1900+ 273 K = 2173 K

exhaust temperature = 430°C = 430 + 273 K = 703 K

fuel = 7.0 × 10^9 cal

work = 1.4 × 10^10 J

to find out

actual efficiency and Carnot efficiency and power output of engine

solution

first we find actual efficiency that is = work / heat input

put the value and

input energy = 7.0 × 10^9 cal (4.184 J/1 cal) = 29.29 × 10^9 J

actual efficiency = 1.4 × 10^10 / ( 29.29 × 10^9 )

actual efficiency = 0.4778

actual efficiency is 47.78 %

and

Carnot efficiency is = 1 - ( 703 / 2173 )

so Carnot efficiency is = 0.67648

Carnot efficiency is 67.65 %

and

power output = work / time

power output = 1.4 × 10^10 / 3600 sec

power output = 3.88 × 10^6 W

power output = 3.88 × 10^6 W / 746 hp

so power output is 5.20 × 10^3 hp

5 0

3 years ago

A wheel starts from rest and rotates with constant angular acceleration to reach an angular speed of 11.2 rad/s in 3.07 s. (a) f

Hitman42 [59]

(a) The angular acceleration of the wheel is given by
$\alpha = \frac{\omega_f - \omega_i }{t}$
where $\omega_i$ and $\omega_f$ are the initial and final angular speed of the wheel, and t the time.

In our problem, the initial angular speed is zero (the wheel starts from rest), so the angular acceleration is
$\alpha = \frac{(11.2 rad/s) - 0}{3.07 s} =3.65 rad/s^2$

(b) The wheel is moving by uniformly rotational accelerated motion, so the angle it covered after a time t is given by
$\theta (t) = \omega_i t + \frac{1}{2} \alpha t^2$
where $\omega_i = 0$ is the initial angular speed. So, the angle covered after a time t=3.07 s is
$\theta= \frac{1}{2} \alpha t^2 = \frac{1}{2}(3.65 rad/s^2)(3.07 s)^2 = 17.2 rad$

6 0

3 years ago

Which of the following measure is more accurate? 500.00kg, 0.0005kg,6.00kg

gavmur [86]

Answer: 500.00kg

Explanation:

3 0

3 years ago

A stone is thrown straight downward with a speed of 20 m/s from the top of a tall building. If the stone strikes the ground 3.0

Lady_Fox [76]

Do you remember this formula for the distance traveled while accelerated ?

<u>Distance = (initial speed) x (t) plus (1/2) x (acceleration) x (t²)</u>

I think this is exactly what we need for this problem.

initial speed = 20 m/s down
acceleration = 9.81 m/s² down
t = 3.0 seconds

Distance down = (20) x (3) plus (1/2) x (9.81) x (3)²

Distance = (60) plus (4.905) x (9)

Distance = (60) plus (44.145) = 104.145 meters

Choice <em>D)</em> is the closest one.

6 0

3 years ago

the minimum flying speee for a bird called a house martin is 9.0ms^-1. it reaches this speed by falling from its nest before swo

Lilit [14]

Answer:

The nest must be about 4.15 meters above ground

Explanation:

Use the velocity equation under accelerated motion (acceleration of gravity ):

$v_f=v_i+a\,*\,t$

which for this case has initial velocity = 0 (falls from the nest), final velocity = 9 m/s, and a = 9.8 m/s^2, then we can find the time needed in air while falling to reach the required speed:

$v_f=v_i+a\,*\,t\\9=0+9.8\,t\\t=\frac{9}{9.8} \, sec\\t \approx 0.92\,\, sec$

We now use this time value to find the distance covered in free fall during 0.92 seconds:

$d=\frac{1}{2} \,9.8 \,t^2=4.9\,(0.92)^2=4.147 \,meters\approx 4.15\,meters$

8 0

3 years ago