Question

A bob attached to a string of length L = 1.25 m, initially found at the equilibrium position, is given an initial velocity v = 0.8 m/s. The maximum displacement angle, θmax, is: (Take g=10 m/s²)

Answer 1

the max height reached is when all the KE is converted to PE, so
v^2 = 2gh
h = 0.8^2/20 = 0.032 m
cosθ = (1.25-0.032)/1.25 = 0.9744
θ = 13°