physics
posted by nm .
A wooden box weighing 281 N is pushed across the floor by a workman who exerts a horizontal force of 166 N. If the force of friction between the box and the floor is 21 N, what is the acceleration (in meters/second^2) of the box?

the force that are acting on the box are1)normal force, gravational force, horizontal force, friction force. If you want to find the a, use the eq of new ton laws. F=MA. For the force you need to add friction force and horizontal force. But you don't know the mass of the object. So u need to find the mass by Nmg=0. After that plug in mass in the first eq and solve it. GOOD LUCK.