Roger N. answered 11/08/21
. BE in Civil Engineering . Senior Structural/Civil Engineer
Solution:
You are given initial velocity V0 = 25 m/s , initial height y0 = 40 m/s and the angle ∝ =0 and need to find the range x of a projectile shot at 0 degrees, x = Vo cos ∝ t , x = 25 m/s cos (0º) t = 25m/s (t)
so you need to find the time, from the height equation of a projectile
y = -1/2 gt2 + V0 sin ∝ t + yo , knowing that the final height of the cannon shot is zero, y = 0
0 = -1/2 gt2 + Vo sin ( 0) + 40 m , 0 = -1/2 gt2 + 40m, 1/2 gt2 = 40 m , 1/2(9.8 m/.s2) t2 = 40 m
t2 = (40m)(2) / 9.8 m/s2 = 8.16 s2 and t = √ 8.16 s2 = 2.85 s
and x = 25m/s ( 2.85 s) = 71.3 m Answer D