A $1 \mathrm{~kg}$ object strikes a wall with velocity $1 \mathrm{~m} \mathrm{~s}^{-1}$ at an angle of $60^{\circ}$ with the wall and reflects at the same angle. If it remains in contact with wall for $0.1 \mathrm{~s}$, then the force exerted on the wall is :