Question

Simple physics problem:
"A free falling body goes through 100 m. Determine at which height the body started falling as well as the time it employs in order to reach the ground. Consider that the body starts from an inertial state and ignore the friction involved."

Answer 1

A free falling body goes through 100 m during the last second*****

Answer 2

You can find the velocity at the beginning of that last second using the following equation:\[s=v _{0}t+\frac{ 1 }{ 2 }g t ^{2}\]where s is the distance (100m), v0 is the original velocity; g is the acceleration of gravity; and t is time (1 sec). Great, you say. What does that get me? Well, now you can find the final velocity of the falling object from this equation:\[v _{f}^{2}=v _{0}^{2}+2gs\]You already have v0, g, and s (100m). We're getting there. Now, what do we do? Well, since we know the body's final velocity, we can write an expression for its kinetic energy. Conservation of energy tells us that the kinetic energy when the object reaches the ground has to equal the potential energy of the object before it started falling:\[mgh _{0}=\frac{ 1 }{ 2 }mv _{f}^{2}\]where m is mass; h0 is the starting height; and vf is the final velocity. We don't know mass, but that's okay because we can simplify this problem to:\[h _{0}=\frac{ v _{f}^{2} }{ 2g}\]. Now we have the starting height. Now all we have to do is find the total time, which is a doodle given the following equation:\[s=h _{0}=\frac{ 1 }{ 2 }g t ^{2}\] Does that help?

Answer 3

did u get it?!

Answer 4

Yeah I understood all the various passages, all I have to do now is to put in the numbers...
Thank you very much for helping me out!! I answered this late cause in my country I have some connection problems.