Answer: C. 12.6
Explanation: 2*pi*1.8= 11.304
11.304/0.9= 12.56
The new gravitation force at the new location is 40 N
Explanation:
The weight of the astronaut is given by the equation
(1)
where
m is the mass of the astronaut
g is the acceleration of gravity
The acceleration of gravity at a certain distance
from the centre of the Earth is given by

where G is the gravitational constant and M is the Earth's mass. So we can rewrite eq.(1) as

When the astronaut is on the Earth's surface,
(where R is the Earth's radius), so his weight is

Later, he moves to another location where his distance from the Earth's surface is 3 times the previous distance, so the new distance from the Earth's centre is

Therefore, the new weight is

Which means that his weight has decreased by a factor 16: therefore, the new weight is

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Water because the light is able to enter the water and allow heat to enter faster.
Explanation:
We have,
Surface area, 
The current varies wrt time t as :

(a) At t = 2 seconds, electrical charge is given by :

(b) Current is given by :

Instantaneous current at t = 1 s is,

(c) Current is, 
Current density is given by electric current per unit area.

Therefore, it is the required explanation.