Question

please answer me..! help pls..!

Answer 1

we know
${v}^{2} = {u}^{2} + 2as$
where, v is the final speed
u is the initial speed
a is the acceleration
s is the distance.

at first v= 30 m/s u=20m/s
and PQ = s
so, 30^2=20^2+2as
or, 2as= 30^2 - 20^2= 500
or, a×s= 250

now, at mid point distance s'= s/2
and if the speed at mid point is v'
then,

(v')^2=u^2 +2as'
or, (v')^2 = 20^2 + 2a×(s/2)
or, (v')^2 = 400+a×s
or, v' = √( 400+250)=√650

thus , option 3 is correct.