50ft.=15.24m
35ft.=10.67m
Potential energy
=mgh=m∗9.81∗15.24=270J
⟹m=1.8kg
a) Initial kinetic energy is 0.
Using conservation of energy;
270+0=Kf+mghf
Kf=270−(1.8∗9.81∗10.67)
=81.59J (Answer)
b) The instant before the brick hits the ground, it's potential energy becomes 0.
Thus, all of its initial energy is converted to kinetic energy.
Hence, final kinetic energy=270J. (Answer)
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