Question

In a javelin throw, an athlete has thrown the javelin vertically upward and reached a height of 100 m. What is the velocity at which it was thrown

Answer 1

Hi there!

We can use the following kinematic equation:

`v_f^2 = v_i^2 + 2ad`

vf = final velocity (0 m/s at the top of the trajectory)
vi = initial velocity (at which it was thrown, ? m/s)

a = acceleration (due to gravity, 9.8 m/s²)

d = displacement of the javelin (100 m)

We can plug in the givens:

`0 = v_i^2 + 2(-9.8)(100)\\\\2(9.8)(100) = v_i^2`

Take the square root to solve:

`v_i = √(2(9.8)(100)) = \boxed{44.27 (m)/(s)}`