A pair of sunglasses fall from a hot air balloon, 225 m above the ground. If air resistance is negligible, calculate a) the time it takes for the sunglasses to reach the ground
b) the sunglasses' final velocity, right before they hit the ground

(a) The glasses are a height y above the ground at time t according to

y = 225 m - 1/2 g t²

where g = 9.80 m/s² is the magnitude of the acceleration due to gravity. They reach the ground when y = 0 :

0 = 225 m - 1/2 g t²

t² = (450 m) / g

t ≈ 6.78 s

(b) The glasses have a velocity v of

v = - g t

so that at the time they hit the ground, they do so with a velocity of

v = - g (6.78 s)

v ≈ 66.4 m/s

the first step is making objective observations.

they have to be based on a certain event and can be confirmed by others if it is right or not.

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 .