a stick is thrown from a cliff 27m high with an initial velocity of 18m/sat an angle of 37 above the horizontial a) use the law of conservation of energy to determine the speed of the stick just before it hits ground b) repeat (a) with an angle of 37 degrees below the horizontial

Question

a stick is thrown from a cliff 27m high with an initial velocity of 18m/sat an angle of 37 above the horizontial a) use the law of conservation of energy to determine the speed of the stick just before it hits ground b) repeat (a) with  an angle of 37 degrees below the horizontial

anonymous · Answer

$\Delta(KE+PE)=0$, i.e. $KE_f+PE_f=KE_i+PE_i.$
Here subscript $f$ means "final" and subscript $i$ means "initial." Also, $KE=\frac{1}{2}mv^2$ and $PE=mgy.$
Here $PE_f=0,$ and $KE_i$ and $PE_i$ are known, so you can solve for $KE_f$, and then for $v_f.$