Question

Mike Powell holds the record for the long jump of 8.95 m, established in 1991. If he left the ground at an angle of 18.8°, what was his initial speed (in m/s)?

Answer 1

Answer:

12 m/s

Explanation:

Projectile Motion

It's also known as 2D motion because the movement takes place in both axis x and y. The x-axis motion is at a constant speed since in absence of friction, no external force stops or accelerates the object. The y-axis motion is at variable speed, which is changed by the acceleration of gravity that makes the object to reach a maximum height and then go back to ground level.

The maximum horizontal distance reached (also called Range) is given by

$\displaystyle X_m=\frac{V_{o}^2sin2\theta}{g}$

Knowing that $\theta=18.8^o, X_m=8.95\ m$, we solve for Vo

$\displaystyle V_o=\sqrt{\frac{gX_m}{sin2\theta}}$

$\displaystyle V_o=\sqrt{\frac{9.8\cdot 8.95}{sin(2\cdot 18.8^o)}}=12\ m/s$

Thus, the initial speed of Mike Powell was 12 m/s