Question

A body is projected upwards with a velocity of 30 ms -1 at
an angle of 30 degree with the horizontal. Determine (a) the time of flight (b)
the range of the body and (c) the maximum height attained by the body.

Answer 1

Time of flight,T = 2usinθ/g
                      = 2*30*sin30°/9.8  (as g = 9.8m/s)
                      =  60/19.6            (as sin30 =1/2)
                      = 3.061 s ≈ 3 s
Maximum Height,H = u²sin²θ/2g
                             = (30)²sin²30°/2*9.8  (as sin²30 = 1/2 * 1/2 = 0.25)
                             =900*0.25/19.6
                             = 225/19.6 = 11.47m
      

Answer 2

(a) time of flight= 2usinα/g
      T = 2*30*sin30/10
      T = 6*1/2 = 3 second
(b) the range of body = u^2sin2α/g
      R = (30)^2sin60/10
      R = 900√3/2*10
      R = 45√3 m
(c) maximum height = (usinα)^2/2g 
      H = (30*sin30)^2/20
      H = 15^2/20
      H = 225/20
      H = 11.25 m