Question

an object starts frim rest and moves with acceleration a=4i.its position after 3s is r=7i+4j.wht is the initial psition?

Answer 1

Acceleration is constant.
u = 0
From equations of motion
s = ut + 1/2 at^2
Let s = x
x = 0 × 3 + 1/2 × 4i × 3×3 + Xo
x = Xo + 8i
y = Yo
Xo + 18 i = 7 I
Xo = - 11 i
Yo = 4 j
Initial position = - 11 i + 4 j

Answer 2

Find your answer in the attachment

Hope it helps