Physics with calc 1 - Answer the (no response) 2.In a game of American football,
ID: 1434128 • Letter: P
Question
Physics with calc 1 - Answer the (no response)
2.In a game of American football, a placekicker must kick a football from a point 36.0 m (about 40 yards) from the goal (distance measured along the ground), and half the crowd hopes the ball will clear (that is, go above) the crossbar, which is 3.05 m high. When kicked, the ball leaves the ground with a speed of 20.0 m/s at an angle of 48.0° to the horizontal.
(a) By how much does the ball clear or fall short of clearing the crossbar? (That is, calculate the height of the ball when it gets to the crossbar, and compare to the height of the crossbar itself. Enter a negative answer if it falls short.)
(b) Does the ball approach the crossbar while still rising or while falling? (Hint: Compute the velocity vector.)
rising or falling?
Explanation / Answer
Vo = 20.0 m/s
Vx = 2300 cos 48.0
Vy = 20.0 sin 48.0
Determine time to reach cross-bar using x- displacement
X = Xo + Vox t + (1/2) at^2
Substituting:
36.0 = 0 + (20.0 cos 48.0) t + 0
t = 2.69 seconds
Determine Y
Y = Yo + Voy t - (1/2)gt^2
Y = 0 + (20.0 sin 48.0)(2.69) - (4.9)(2.69)^2
Y = 4.524 m
The ball clears the cross bar by (4.52 - 3.05) = 1.47 m
When Vy = 0, the ball is at maximum height
So using: V= Vo + at
0 = (20.0 sin 48.0) - 9.8 t
t = 1.516 seconds
So if t< 1.516 seconds ball is rising
if t > 1.516 seconds, ball is falling
Since t = 2.69 seconds which is > 1.516 seconds, ball is falling