a 10-kg rock and a 20-kg rock are dropped at the same time and experience no significant air resistance. if the 10-kg rock falls with acceleration a, what is the acceleration of the 20-kg rock?

Answer 1

as Galileo showed, it is the same for all objects (ignoring air resistance).

Since F = ma, and a 20kg object weighs twice as much as a 10kg object,

2F = (2m)a

but a remains the same.