Five forces −→F1, −→F2, −→F3, −→F4 and −→F5 are acting on a particle of mass 2.0 kg so that it is moving with 4 m/s2 in east direction. If −→F1 force is removed then the acceleration becomes 7 m/s2 in north. Find the magnitude of acceleration of the block if only −→F1 is acting.