Q.

A projectile is given an initial velocity of  (i^+2j^)m/s, where i^ is along the ground and j^ is along the vertical. If g=10 m/s2, the equation of its trajectory is:       [2012]

1 y=x-5x2  
2 y=2x-5x2  
3 4y=2x-5x2  
4 4y=2x-25x2  

Ans.

(2)

From equation, v=i^+2j^    

x=t                                                  ...(i)

y=2t-12(10t2)                                ...(ii)

From (i) and (ii), y=2x-5x2