Question

how to solve using calculus?

Answer 1

tricky as the problem is trivial calculus - wise

do you mean start with F = ma and so \(a = \dfrac{F}{m} \implies v = \frac{F}{m}t + C\) as \(a = const\).??

the solution included uses the equations of motion, which can be derived from calculus but are usued, again, because the problems are trivial in that regard.

maybe i am missing something

Answer 2

Try a=g sin theta to find acceleration ....and 2aS=Vf^2 - Vi^2 to find Vf...