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Science-Related Homework Help Physics Topic started by: rizzamella on Oct 21, 2012



Title: How do you do this projectile motion problem?
Post by: rizzamella on Oct 21, 2012
To win the game, a place kicker must kick a football from a point 31 m (33.9016 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 19 m/s at an angle of 40.7? from the horizontal. The acceleration of gravity is 9.8 m/s2 .

By how much vertical distance does the ball clear the crossbar? Answer in units of m.


Title: How do you do this projectile motion problem?
Post by: inquirytobio on Oct 21, 2012
horizontal motion:
x = (vx)(t)
x = (vo*cos?)(t)
31 = (19*cos40.7?)(t)
t = 2.152 s

vertical motion:
y = (voy)(t) - gt^2/2
y = (vo*sin40.7?)(t) - gt^2/2
y = (19*sin40.7?)(2.152) - (9.8)(2.152)^2/2
y = 3.97 m

Since the crossbar is 3.05 m high, the ball goes
3.97 - 3.05 = 0.92 m
higher than the bar.