Randall D. Knight — Kinematics in Two Dimensions: Problem Problem_58

A javelin thrower standing at rest holds the center of the javelin behind her head, then accelerates it through a distance of $70\text{ cm}$ as she throws. She releases the $600\text{ g}$ javelin $2.0\text{ m}$ above the ground traveling at an angle of $30^\circ$ above the horizontal. Top-rated javelin throwers do throw at about a $30^\circ$ angle, not the $45^\circ$ you might have expected, because the biomechanics of the arm allow them to throw the javelin much faster at $30^\circ$ than they would be able to at $45^\circ$. In this throw, the javelin hits the ground $62\text{ m}$ away. What was the acceleration of the javelin during the throw? Assume that it has a constant acceleration.