Answer:

Explanation:
We are given that
Gravitational force=
r=0,U(0)=0
We know that
Gravitational potential energy=


Substitute r=0 ,U(0)=0


Substitute the value

Answer:
B. Water and sugar.
Explanation:
In the given options water and sugar would be the poor conductor of electricity. Other given options such as water and salt, water and Hcl and water and NaOH are better conductor of electricity because Hcl ,NaOH, salt (Nacl) can break into their ionic form whereas water and sugar will not.
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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