posted by Roger on .
A place kicker must kick a football from a point 25.5 m from the goal, and must clear a crossbar that is 3 m off the ground. When kicked the ball leaves the ground with a speed of 21.9 m/s at an angle of 54o to the horizontal. By how much does the ball clear the crossbar?
The bar reaches the goal post in time
t = 25.5/(Vo*cos54) = 1.981 seconds
Vo is the initial velocity of the football.
Calculate the height of the ball at that time, using the appropriate formula (which you should know or derive),
y = Vo*sin54*t - (g/2)*t^2
= 35.10 - 19.23 = 15.87 m
and subtract 3 m from that.