In this case we have u=4i , a=09i+07j and r0=400i+350j.
Substituting these into the equation r=ut+21at 2+r0 gives the position vector of the ball at time 10 as:
r=(4i)t+21(09i+07j)t 2+1.5j=8ti+2tj−5t 2j+1.5j=(8t)i+(1.5+2t−5t 2)j m
9i+07j9i+07j)t 2+1.5j=8ti+2tj−5t 2j+1.5j=(8t)i+(1.5+2t−5t 2)j m