A placekicker must kick a football from a point 36.0 m ( about40 yards) from the

Question

A placekicker must kick a football from a point 36.0 m ( about40 yards) from the goal, and half the crowd hopes the ball willclear the crossbar, which is 3.05 m high. when kicked, the ballleaves the grouind with a speed of 20.0 m/s at an angle of 53.0 tothe horizonta. A) by how much does the ball clear from or fall short ofclearing the crossbar( be sure to indicate in your answer whetherclears it or not) B) does the ball approach the crossbar while still rising orwhile falling? C) What is the maximum height reached by the football? A placekicker must kick a football from a point 36.0 m ( about40 yards) from the goal, and half the crowd hopes the ball willclear the crossbar, which is 3.05 m high. when kicked, the ballleaves the grouind with a speed of 20.0 m/s at an angle of 53.0 tothe horizonta. A) by how much does the ball clear from or fall short ofclearing the crossbar( be sure to indicate in your answer whetherclears it or not) B) does the ball approach the crossbar while still rising orwhile falling? C) What is the maximum height reached by the football?

Explanation / Answer

initial horizontal velocity=20*cos53 horizontal acceleration=0 horizontal distance=36 m let the ball took t s to cover 36 m 36=20*cos53*t t=2.99 s initial vertical velocity=20*sin53 vertical acceleration=g=9.8 let max. vertical reached by the ball=H in T s. v=u-g*t 0=20*sin53-9.8*T T=1.63 s v2=u2-2*g*H 0=(20*sin53)2-2*9.8*H H=13.02 m in (2.99-1.63)=1.36 let the ball fell h m from the max. height u=0 h=u*t+(1/2)*h*t2 h=0+(1/2)*9.8*1.362 h=9.06 m when the ball passes the cross bar it is (13.02-9.06)=3.96 m abovethe ground the ball clears the crossbar by (3.96-3.05)=0.91 m the ball approaches the cross bar while falling the max height reached by the ball=13.02 m

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