Not sure what your question means but the nearest star is Alpha Centauri which is about 4.2 light years (ly) away. This is roughly 4x10¹³ km away. A billion is 10⁹ so this is 4x10⁴ larger than a billion. I'd say the last one then...
Answer:
Two forces that act in opposite directions produce a resultant force that is smaller than either individual force. To find the resultant force subtract the magnitude of the smaller force from the magnitude of the larger force. The direction of the resultant force is in the same direction as the larger force.
Answer:

Explanation:
The torque of a force is given by:

where
F is the magnitude of the force
d is the distance between the point of application of the force and the centre of rotation of the system
is the angle between the direction of the force and d
In this problem, we have:
, the force
, the distance of application of the force from the centre (0,0)
, the angle between the direction of the force and a
Therefore, the torque is

Answer:
Explanation:
There will not be any internal reflection . it will be only refraction
critical angle = θ
Sinθ = 1 / μg
μg = 1.43 / 1.33 =
Sinθ = 1.33 / 1.43
= .93
θ = 68.44
angle of incidence i = 68.44 / 2
= 34.22
Sin i / Sin r = μw = 1.33 / 1.43
= .93
sin 34.22 / sinθ₁ = .93 , θ₁ is angle of refraction.
sinθ₁ = sin 34.22 / .93
= .5623 / .93
= .6047
θ₁ = 37 degree Ans
Answer:
C. 
Explanation:
Let initial charges on both spheres be,

When the sphere C is touched by A, the final charges on both will be,
#Now, when C is touched by B, the final charges on both of them will be:

Now the force between A and B is calculated as:

Hence the electrostatic force becomes 3F/8