Why does the plastic ball have less acceleration due to gravity?
I understand things best mathematically, so bear with me. Each of the balls actually has TWO forces acting on it: 1. downward force due to gravity, in the amount “mg” (“m” is different for each ball); 2. upward force due to air friction. If all the balls are roughly the same size and shape, then the amount of air friction is roughly proportional to the ball’s SPEED, and doesn’t depend on its mass. So the upward force due to air friction is “kv”, where “k” is some (unknown) constant, and “v” is the ball’s speed. So, as “Ball 1” falls, it has this much net force on it: F1 = (downward force)−(upward force) F1 = (m1)g – kv And its acceleration is this much (by Newton’s 2nd Law): a1 = (F1)/(m1) a1 = ((m1)g – kv) / (m1) a1 = g – kv/(m1) Same kind of thing for Balls 2 and 3: a2 = g – kv/(m2) a3 = g – kv/(m3) What this says is: None of the balls falls at exactly rate “g”; each is reduced a bit, by an amount “kv/m” where “m” is the particular mass of the ball. In cases where “m” is large (like
