What is the physics involved in achieving the maximum range when throwing the javelin?

The physics involved in achieving the maximum range and the forces acting on the javelin are no different from those found when throwing any other projectile. Air resistance and gravity are the primary forces working against the javelin in flight. The air resistance is very small, because a javelin is designed to be aerodynamic.

Gravity is working to pull the javelin back towards the ground. Although this does not affect the javelin's horizontal motion directly, the javelin is more likely to land sooner if it is launched at an angle that is very close to the ground, or conversely, an angle that is too close to vertical.

The optimum release angle for any thrown object is 45 degrees, or exactly halfway from the horizontal to the vertical. The relatively simple geometry used to prove this statement can be found in any fundamental text dealing with kinematics. The javelin rotates about its long axis as it travels through the air, a feature that helps to keep it stable in flight — just like the rifling in the barrel of a gun that causes the bullet to spin.

Source : The Hindu