\(PQ = s\)

Using, \(v^{2}=u^{2}+2\) as.

\(\Rightarrow 40^{2}=30^{2}+2 a s\)

\(\Rightarrow 2\) as \(=700\Rightarrow\) as \(=350\)

Now, assume velocity of car at a midpoint of \(PQ\) is \(V\). \(V ^{2}= vp ^{2}+2 a \left(\frac{ s }{2}\right)\)

\(\Rightarrow V^{2}=900+350=1250\)

\(\Rightarrow V =35.35\;{ m }/{ s }\)

OR

\(V_{\text {mid }}=\sqrt{\frac{V_{p}^{2}+V_{Q}^{2}}{2}}\)

\(V_{m i d}=\sqrt{\frac{30^{2}+40^{2}}{2}}\)

\(V_{mid} =\sqrt{\frac{900+1600}{{2}}}\)

\(V_{{mid}}=\sqrt{\frac{2500}{2}}\)

\(V_{{mid }} =25 \sqrt{2} m / s\)