PreAp Physics
posted by Maria on .
To win the game, a place kicker must kick a
football from a point 17 m (18.5912 yd) from
the goal, and the ball must clear the crossbar,
which is 3.05 m high. When kicked, the ball
leaves the ground with a speed of 15 m/s at
an angle of 58.9
◦
from the horizontal.
The acceleration of gravity is 9.8 m/s
2
.
By how much vertical distance does the ball
clear the crossbar?
Answer in units of m

The horizontal compoent of the football's velocity is and remains, 15.0 cos58.9 = 7.748 m/s
The time it takes the ball to reach the goal post is therefore
t = 17.0/7.748 = 2.19 seconds
Now use that time t to calculate the distance of the ball about the ground at that time, y.
y = 15.0 sin58.9*t 4.9 t^2
= 12.84 t  4.9 t^2 = ___ m
Is the answer more or less than 3.0 meters? Calculate it and see for yourself.