At what height from the earth, g becomes
?
a)g/2
b) 0.414 r
d) r
c) 0.7 r

Explanation:

Near the surface of the Earth (sea level), gravity decreases with height such that linear extrapolation would give zero gravity at a height of one half of the Earth's radius - (9.8 m. s−2 per 3,200 km.)

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .

f=ma newton

f=100x2.5=250n