Marquette King, formerly of the Denver Broncos, is practicingkicking off using a kicking holder with the ball on the ground. For one of the kicks the ball reaches a height of 90.6 m andlands on the ground 53 yds (48.5 m) away. Find the magnitudeof the initial velocity given by his kick to the ball. Treat airresistance as negligible. Hint: Even though the horizontal andvertical motions are independent, there is a quantity that iscommon to both of them.

Explanation:

Maximum height reached = 90.6 m . Range = 48.5 m

. Let u be the initial velocity at angle α .

Horizontal range is covered by horizontal component of u .

Vertical height is achieved by vertical component

v² = u² sin² α - 2gh , t is time taken to attain maximum height .

0 = u² sin² α - 2 x 90.6 x 9.8  

u² sin² α = 2 x 887.88  ( 1 )

Range R = u² sin2α / g

48.5 = 2 u² sinα . cos α / 9.8

u² sinα . cos α = 237.65  ( 2 )

( 1 ) / ( 2 )

Tan α = 2 x 887.88 / 237.65 = 7.47

α = 82⁰

u² sin² α = 2 x 887.88

u² sin² 82 = 2 x 887.88

u² = 1812

u = 42.56  m /s