The discussion centers on calculating the initial velocity of a football that starts 64 yards from a goal post and barely clears a 10-foot high bar at a 43-degree angle. The relevant kinematic equation used is (vf)^2 = (vi)^2 + 2a(x), where 'a' is the acceleration due to gravity. Participants emphasize the importance of using consistent units, noting that 9.8 m/s² is approximately 32.2 ft/s², which is crucial for accurate calculations.
PREREQUISITESStudents in physics courses, educators teaching kinematics, and anyone interested in solving projectile motion problems.
What, precisely, does vi represent in that equation?md3v said:(vf)^2 = (vi)^2 + 2a(x)
(0) = (vi)^2 + 2(-9.8)(10)
Be careful here. The height of the bar which the football clears is measured in feet. The distance the ball starts from the goal is measured in yards. You have g measured in m/s2. Pick a unit system and put everything in consistent units. BTW, 9.8 m/s2 ≈ 32.2 ft/s2md3v said:Homework Statement
A football started on the ground 64 yards from the base of the goal post and barely clears the 10 ft high bar. The initial trajectory of the football was 43 deg above the horizontal. What was its initial speed?
Homework Equations
The Attempt at a Solution
(vf)^2 = (vi)^2 + 2a(x)
(0) = (vi)^2 + 2(-9.8)(10)