Question

When a stone of mass 50kg and another of mass 5kg fall down simultaneously from the top of a five-storey building, which one will reach the ground first?

Answer 1

When we place the mass side by side and drop them we need to establish the force applied on the mass when the mass is dropping from a certain height. Using the formula of kinematics we need to determine as to how the velocity of the objects are dependent on the other factors like mass, acceleration and height.

Complete solution:
When two masses of different weight fall down under the influence of gravity or when the heights of the down fall is unknown and the formula of kinematics which doesn't have the mass in any of the formula rules out the introduction of mass in the free falling of the two stones. The concept of freefalling of objects means that the objects are falling under the sole influence of gravity and have no air or negligible air resistance.

And when the object is falling under the influence of gravity or free-fall, the object experiences weightlessness as if floating in space making the mass of the object useless. Therefore, when a stone of mass 50kg and 5kg falls freely without any external force influence both the stones will fall at a same velocity or one should say under the same acceleration that is the acceleration due to gravity $g=9.8m/{{s}^{2}}$.

Note: Students may go wrong if they use the formulas of kinematic like ${{v}^{2}}={{u}^{2}}+2aS$ or $S=ut+\dfrac{1}{2}a{{t}^{2}}$ or $v=u+at$ as most of the variables are unknown like distance, time and initial velocity. Hence, the usage of mass in either of the three formulas will do no good and velocity will be incalculable.