"50ft.=15.24 m"
"35ft.=10.67m"
Potential energy
"=mgh=m*9.81*15.24=270J"
"\\implies m= 1.8kg"
a) Initial kinetic energy is 0.
Using conservation of energy;
"270+0=K_f+mgh_f"
"K_f=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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