in the above equation the relationship between body frame components of the reaction forces and inertial frame components of reaction forces is used. the assumption that the bar connecting the point mass to the cart is massless implies that this bar cannot transfer any load perpendicular to the bar. thus, the inertial frame components of the reaction forces can be written simply as formula_66 which signifies that the bar can only transfer loads along the axis of the bar itself. this gives rise to another equation which can be used to solve for the tension in the rod itself