Answer:
Centre of mass is the point at which the distribution of mass is equal in all directions, and does not depend on gravitational field. Centre of gravity is the point at which the distribution of weight is equal in all directions, and does depend on gravitational field.
Answer:
a) solar activity -- sudden eruptions of large bubbles of plasma and magnetic energy
and
d) solar flare -- sudden release of magnetic energy
Explanation:
We can start by eliminating the options that are definitely wrong.
A coronal mass ejection is not a relatively cool spot on surface of the sun, in fact such a spot is a sunspot, while a coronal mass ejection occurs when the magnetic field of the sun emerges as a loop. Thus, both options B and E are incorrect, leaving only A, C, and D. Option C makes no sense, as the sun's gravitational field does not 'churn'. Thus, only options A and D are left. A closer look at A and D reveals they are correct; solar flares are in fact sudden releases of magnetic energy, as seen in this quote from UC Berkeley's website; "Solar flares are caused by sudden changes of strong magnetic fields in the Sun's corona.". And solar activity is a blanket term for the effects of eruptions of plasma and magnetic energy from the sun.
The power expended is 500 W
Explanation:
First of all, we start by calculating the work done by the man in order to ascend: this is equal to the gravitational potential energy gained by the man, which is

where
m = 50 kg is the mass of the man
is the acceleration of gravity
is the change in height
Substituting,

Now we can calculate the power expended, which is given by

where
W = 2500 J is the work done
t = 5 s is the time elapsed
Substituting, we find

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Answer:
the last one
Explanation:
Because it is a magnifying glass, it magnifies the object and makes it bigger than it appears
Answer:
2.73414 seconds
467622.66798 J
Explanation:
t = Time taken
u = Initial velocity
v = Final velocity
s = Displacement
g = Acceleration due to gravity = 9.81 m/s² = a



or

The time taken is 2.73414 seconds
The potential energy is given by

The change in potential energy is 467622.66798 J