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I have been trying to figure the following problem out but unfortunately I have not had any obvious success. It is about Kinetic Energy:

A stone is falling from the roof of a house down to the ground. In the last second of the fall, the stone's energy increases of 293 J.

How high is the house?

(friction is neglected)

I have gone several ways but never got the stated result of 20,06 m.

I would be very happy if anyone could give me a hint to solve this one. It seems so easy but I cannot make it :(

The most logical way - at least for me - would be: (the ground is zero in my coordinate system)

âˆ†Ekin= 293 J = 1/2 * m * v^2 thus: V= - 17,13 m/s

V is the velocity on average in the last second. Thus the calculated velocity is actually there at tf-0,5s. With Tf is meant the over all time of the fall.

V= - g*t, thus t= 1.745 s

tf= t + 0.5 s = 2,245 s

h= 1/2*g*t^2= 24,72 m

Any suggestions ?

I would be really happy to get some help with this one !

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# Kinetic Energy: It sounds simple but I have been having a very hard time

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