Verified answer

1.

Since the earth pulls all objects with forces which are proportional to the masses of the objects, In other words earth pulls all objects with the same acceleration irrespective of their masses.

{Note that one cannot answer why objects fall at the same rate. It is nature.}

It is a discovery that all objects fall with the same rate.}

2.

Acceleration as per Newton’s second law is that a = Force / mass.

When there is no resistance a = g = F/ m where F is the weight of the object when there is no air resistance.

If there is resistance the force acting on the object will be less by the amount of resistance

a = F1 / m = (F – f) / m = F/m – f/m = g – (f/ m) where f is the force of resistance.

Thus the acceleration is reduced from g by a value equal to the acceleration due to the air resistance.

3.

The weight scale reading will not change if the elevator moves up and down with constant velocity.

It will be affected only if there is an upward or downward acceleration of the elevator.

If there is a net force upward or down ward on the elevator it will have an acceleration a

a which is greater than the value of g or less than g .

As shown in 2, a = g ±a’ where a is the acceleration due to the force greater or less than the weight mg .

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