What is the answer to this definition ?
in the second law of motion it is mass x acceleration. the ability to apply a change in velocity on a given object.
a force
b friction
c unbalanced forces
d none of the above, tell what it is

Ahot-air balloon takes off from the ground traveling vertically with a constant upward acceleration of magnitude g/4. after time interval δt, a crew member releases a ballast sandbag from the basket attached to the balloon. how many seconds does it take the sandbag to reach the ground? (express your answer in terms of δt)