To practice tactics box 10.1 calculating the work done by a constant force. to find the work done on an object by a force, begin with a visual overview and follow tactics box 10.1. recall that the work w done by a constant force f⃗ at an angle θ to the displacement d⃗ is w=fdcosθ. the vector magnitudes f and d are always positive, so the sign of w is determined entirely by the angle θ between the force and the displacement.