Question

A body projected with velocity 30m/s reaches its maximum height in 1.5s.Its range is

Answer 1

u = 30 m/s       Ф = angle of projection.

time to reach maximum height =  u sinФ / g = 1.5 sec given.
 So  sinФ = 1.5 * 10 /30 = 1/2   
  So Ф = 30 deg.

Range =  u² Sin2Ф / g  =  30² * sin60 / 10  = 45 √3 m

Answer 2

Given,
v = 30 m/s       
Ф = ?
Its given....Reaches its maximum height in 1.5s
Then, sinФ = 1.5 × 10 /30 = 1/2   
 ∴ Ф = 30°

Now we know range formula:
Range =  v² Sin2Ф / g  
            =  30² × sin60 / 10  
            = 45 √3 m