Let in is body reaches upto point
A and after two more second, it reaches upto point
BTotal time of ascent for a body is,
t‌ascent ‌‌=2+1=3st‌ascent ‌‌=‌=‌‌‌=3⇒usin‌45∘=30‌‌...Horizontal component of velocity remains always constant,
u‌cos‌45∘=v‌cos‌45∘For vertical upward motion between point
O and
A,
‌vy=uy−gt‌vsin‌45∘=usin‌45∘−10×1‌‌=30−10‌‌‌ from Eq. (i) ‌‌v=20√2m∕sPutting this value in Eq. (ii),
u‌cos‌45∘=20√2×‌=20From Eq. (i) and Eq. (iii),
‌u2sin‌245∘+u2cos245∘=(30)2+(20)2‌u2=1300‌u=10√13m∕s