In U.S. football, after a touchdown the team has theopportunity to earn one more

Question

In U.S. football, after a touchdown the team has theopportunity to earn one more point by kicking the ball over the barbetween the goal posts. The bar is 10.0 ft above the ground, andthe ball is kicked from ground level, 36.0 ft horizontally from thebar, see figure below. Football regulations are stated in Englishunits, but convert to SI units for this problem.

3_______ km/h In U.S. football, after a touchdown the team has theopportunity to earn one more point by kicking the ball over the barbetween the goal posts. The bar is 10.0 ft above the ground, andthe ball is kicked from ground level, 36.0 ft horizontally from thebar, see figure below. Football regulations are stated in Englishunits, but convert to SI units for this problem. (a) There is a minimum angle above the groundsuch that if the ball is launched below this angle, it can neverclear the bar, no matter how fast it is kicked. What is thisangle? 1 degree (b) If the ball is kicked at 64.4 degree above the horizontal, what must its initial speed be if it to justclear the bar? Express your answer in m/s and km/h. 2 ______ m/s 3_______ km/h

Explanation / Answer

First change the units to metric 36ft = 10.973m 10ft = 3.048m for the x component, we have d=v*t (becomes 10.973 = v * cos( 64.4) * t) for the y component we have d=v*t + 1/2 * a *t^2 (becomes 3.048 = v * sin(64.4) * t + 1/2 *-9.8 * t^2) re-arrange the x component equation for t and sub into the otherequation, leaving us with 3.048=v*cos(64.4)*(10.973/v*sin(64.4))-4.9(10.973/v*sin(64.4))^2 now solve for v (re arrange equation to get -9.1194*v^2 =-725.429) You'll get an answer of 8.92 m/s or 32.112 km/h

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