( 2 ) Two workers push horizontally in the same direction on a 250 - kg wooden crate that is on a wooden floor . ( a ) What total force must they exert to start the crate moving ? ( b ) Once moving , one worker exerts a force of 500 N and the other exerts a force of 600 N. Calculate the acceleration of the crate . μk = 0.3 and μs = 0.5