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Vera_Pavlovna [14]
3 years ago
12

Zorch, an archenemy of superman, decides to slow earth's rotation to once per 27.4 h by exerting an opposing force at and parall

el to the equator. superman is not immediately concerned, because he knows zorch can only exert a force of 3.98 ✕ 107 n (a little greater than a saturn v rocket's thrust). how long in seconds must zorch push with this force to accomplish his goal? (this period gives superman time to devote to other villains.)
Physics
1 answer:
lapo4ka [179]3 years ago
8 0
If we assume that Earth is a solid sphere, then I = (2/5)mr² = (2/5) * 5.98e24kg * (6.371e6m)² = 9.71e37 kg·m² 
torque τ = Iα, but also τ = F*r = 3.98e7N * 6.371e6m = 2.54e14 N·m Since τ = τ, 2.54e14 N·m = 9.17e37kg·m² * α α = 3.61e-23 rad/s² 
ωo = 2πrads / (24h*3600s/h) = 7.27e-5 rad/s ω1 = 2πrads / (28h*3600s/h) = 6.23e-5 rad/s 
Plug in numbers t = 2/5 * (5.98 * 10^24 kg) * (6.37*10^6 m) * (7.27 * 10^-5 rad/s - 6.23 * 10^-5 rad/s) / (3.98*10^7 N) = 3.98*10^22 s = 1.26*10^17 yrs
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Jada is rowing a boat across a river that has a current of 5 m/s in the ˆ j direction. Leanne, standing on the shore, observes J
olchik [2.2K]

Answer: d. 8.25 m/s

Explanation:

We are given that Current= 5 m/s in j direction

Velocity= 8 m/s i + 3 m/s j

Now, we have to find Jada's speed with respect to the water.

First we find Jada's velocity with respect to water

v= (8 i + 3 j) - (5 j)

v= 8i - 2 j

To find the speed, we take the magnitude of this velocity vector we have

|v|= \sqrt{(8)^2+(-2)^2}

|v|= \sqrt{68} = 8.246 m/s

which comes out to be around = 8.25 m/s

So option d is correct.

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3 years ago
When a court has "___ ___" they can hear a case once a lower court has ruled on it.
notka56 [123]
Your answer is going to be Appellate jurisdiction.
3 0
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Which question cannot be answered using scientific methods?
serg [7]

Answer:

Questions that cannot be answered through scientific investigation are those that relate to personal preference, moral values, the supernatural, or unmeasurable phenomena.

3 0
3 years ago
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A small block with mass 0.0400 kg slides in a vertical circle of radius 0.600 m on the inside of a circular track. During one of
Maurinko [17]

Answer:

Explanation:

Given that

The mass of the body is 0.04kg

M=0.04kg

The radius of the paths is 0.6m

r=0.6m

The normal force exerted at A is 3.9N

Fa=3.9N

The normal force exerted at B is 0.69N

Fb=0.69N

Then work done by friction from point A to B will be the change in K.E

W=∆K.E+P.E

So we need to know the velocity at both point A and B

Then since the centripetal force is given as

Ft=mv²/r

Then,

For point A

Fa=mv²/r

3.9=0.04v²/0.6

3.9=0.0667v²

v²=3.9/0.0667

v²=58.5

v=√58.5

v=7.65m/s

Va=7.65m/s

Now at point B

Fb=mv²/r

0.69=0.04v²/0.6

0.69=0.0667v²

v²=0.69/0.0667

v²=10.35

v=√10.35

v=3.22m/s

Vb=3.22m/s

Then, the work done is

W=∆K.E+P.E

P.E is given as mgh

The height will be 2R =1.2m

P.E=mgh

P.E=0.04×9.81×1.2

P.E=0.471J

Final kinetic energy at B minus initial kinetic energy at A

W=K.Eb-K.Ea

K.E is given as 1/2mv²

W=1/2m(Vb²-Va²) +P.E

W=0.5×0.04(3.22²-7.65²) +0.471

W=0.5×0.04×(-48.1541) +0.471

W=-0.96+0.471

W=-0.49J

work was done on the block by friction during the motion of the block from point A to point B is 0.49J.

Friction opposes motions and that is why the work done is negative

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3 years ago
a horse began running due east and covered 25km in 4.0 hours what is the average velocity of the horse
Komok [63]

25km / 4hr = <em>6.25 km/hr east</em>

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3 years ago
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