∴ Acceleration of aeroplane w.r.t. the earth, aA→E=5m∕s2 Acceleration of stone w.r.t. the earth, aS→E=−10m∕s2 or aE→S=−aS→E=10m∕s2 Thus, acceleration of aeroplane w.r.t. the stons, aA→S=aA→E+aE→S=5+10=15m∕s2 ∴ Relative separation between the stone and aeroplane in 2s, s=