VectorPlot[{1,9.8 - y/5},{x,0,10},{y,0,60},VectorStyle->Arrowheads[0]]

Manipulate[Show[VectorPlot[{1,9.8 - (γ/m)*y},{x,0,10},{y,0,60},VectorStyle->Arrowheads[0]]],
Style["dy/dx = x + (γ/m)*y",Bold],
{{m,10,"m"},5,25,Appearance->"Labeled"},{{γ,2,"γ"},0,10,Appearance->"Labeled"}]