In Canadian football, after a touchdown the team has the opportunity to earn one
ID: 1528496 • Letter: I
Question
In Canadian football, after a touchdown the team has the opportunity to earn one more point by kicking the ball over the bar between the goal posts. The bar is 10.0 ftabove the ground, and the ball is kicked from ground level, 36.0 ft horizontally from the bar in (Figure 1) . Football regulations are stated in English units, but convert to SI units for this problem. a) If the ball is kicked at 39.0 above the horizontal, what must its initial speed be if it is just to clear the bar? Express your answer in m/s. b) What is the speed in km/hr?
Explanation / Answer
here,
height , y = 10 feet = 3.048 m
horizontal distance , x = 36 ft = 10.97 m
theta = 39 degree
a)
let the initial speed be u
using equation of trajectory
y = x * tan(theta) - g*x^2 /(2*u^2 * cos^2(theta))
3.048 = 10.97 * tan(39) - 9.8*10.97^2 /(2*u^2 * cos^2(39))
solving for u
u = 12.9 m/s
the initial speed is 12.9 m/s
b)
the initial speed , u = 12.9 m/s = 46.44 km/h