Please explain thank you so much. A place-kicker must kick a football from a poi
ID: 1326863 • Letter: P
Question
Please explain thank you so much.
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 23.5 m/s at an angle of 52.5° to the horizontal.
(a) By how much does the ball clear or fall short of clearing the crossbar? (Enter a negative answer if it falls short.)
(b) Does the ball approach the crossbar while still rising or while falling?
Explanation / Answer
A)
Vertical compoennet of velocity = 23.5 sin 52.5
= 18.64 m/s
Horizontal compoenet of velocity = 23.5 cos 52.5
= 14.3 m/s
Time taken to cover 36 m horizontally = 36/14.3 = 2.52 s
Let us calculate height of the ball at time 2.52 s
h = vyi*t - 0.5*g*t^2
= 18.64*2.52 - 0.5*9.8*(2.52)^2
= 15.9 m
It will not clear the cross bar.
B)
time of flight= 2*v* sin 52.5 /g
= 2*23.5 * (sin 52.5) /9.8
= 3.8 s
Time taken is greater than half of time of flight, ball approaches cross bar while falling.