By Newton's second law, the net force on the object is
∑ F = 10.0 N + F = (7.0 kg) (1.0 m/s²)
where F is the unknown force. Since the object is accelerating to the east, F must be acting in the same or opposite direction as the known force that is also directed eastward. Solve for F :
10.0 N + F = 7.0 N
⇒ F = - 3.0 N
which is to say, F has magnitude 3.0 N and points toward the west.
