Question

A high school kicker makes a 34.0yd field goal attempt (in American football) and hits the crossbar at a height of 12.0ft . What is the magnitude of the net displacement of the football from the time it leaves the ground until it hits the crossbar? What is the direction of the net displacement of the football from the time it leaves the ground until it hits the crossbar? Assuming the football took 2.70s to hit the crossbar, what was the magnitude of its average velocity? What was the direction of its average velocity? Explain why you cannot determine its average speed from these data.

Answer 1

What is the magnitude of the net displacement of the football from the time it leaves the ground until it hits the crossbar?
horizontal distance to the crossbar = length f the field = 34yd = 102 ft
vertical distnce to the crossbar = 12 ft
so net displacement = root(12²+102²) = 102.7 ft

Assuming the football took 2.70s to hit the crossbar, what was the magnitude of its average velocity?

Total displacement occured = 102.7 ft in time 2.7 sec
so average veocity = 102.7/2.7 = 38.04 ft/sec

What was the direction of its average velocity?

direction of average velocity = tan^-1(12/102) = 6.71⁰ wrt ground

Explain why you cannot determine its average speed from these data.
From the given data we cannot determine the total distance travelled by the ball. The ball can reach the crossbar in defferent paths according to the initial velocity and the angle of projection (kick)
because of this we cannot determine the avarage speed of the ball