1. The problem statement, all variables and given/known data Find out the amount of force exerted by the screwjack/motor to lift the spill door upwards. The length of the different linkages is known as well as an estimate of the weight of the spill door. 2. Relevant equations Torque = Force x Distance 3. The attempt at a solution All I could think of doing is use the formula T= F*d; using the weight of the spill door as the Force required while the distance is simply the vertical distance between Linkage 1 and 4 - thus ignoring the horizontal linkages. Is this a good/correct approximation? Please let me know or point me towards a correct solution/theory to solve this. Assuming there is no resistance/friction between the different linkages.