A place-kicker must kick a football from a point 36.0 m (about 40 yards) from th

Question

A place-kicker must kick a football from a point 36.0 m (about 40 yards) from the goal. Half the crowd hopes the ball will clear the crossbar, which is 3.05 m high. When kicked, the ball leaves the ground with a speed of 23.6 m/s at an angle of 48.0° to the horizontal.
(a) By how much does the ball clear or fall short (vertically) of clearing the crossbar? (Enter a negative answer if it falls short.)
m

(b) Does the ball approach the crossbar (and cross above or beneath it) while still rising or while falling?
rising
falling

Explanation / Answer

Horizontal velocity = 23.6 cos 48=15.39 m/s apprx

initial vertical velocity = 23.6 sin48= 17.54 m/s apprx

a) Time to reach 36 m = 36/ 23.6cos 48 = 2.339 sec apprx

height covered durin thsi time

h = 17.54*( 2.339 ) - 0.5g(2.339)^2 = 14.213 m apprx

b) the ball will definitely clear the cross - bar by 14.213 - 3.05= 11.163 m apprx

the ball is still rising when it raeches the cross bar

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