A worker must carry 25 kg bags of sand from a packing machine to a dispatch zone (approximately 10 m in distance). When carried upright, the centre of gravity (COG) of the bag is approximately 15 cm from the lumbosacral (LS) joint. The same worker is then tasked with carrying 25 kg bags of feather. The bags are stored in the bottom shelf and the worker must hunch down to pick up the bag. You found that the COG of the bag in this position is approximately 70 cm from the LS joint whereas the COG of the upper body is then located 20 cm from the LS joint. How do you calculate the total compressive force on the spine at L5/S1 if the upper body of the worker is 30 kg and the back muscles act at an average distance of 5 cm from the fulcrum at the L5/S1 junction for the two scenarios above ?

The thin-walled cylindrical can with a spherical dimple weighs 0.2 lb. Determine the force P required to push the can into water to a depth of 8 in. Use =0.036lb/in.3 for water.

Determine the horizontal force P that would keep the uniform 12-kg rectangular plate in the position shown.

The high-pressure water cock is rigidly attached to the support at D. Neglecting the weights of the members, draw the FBD of the entire assembly and count the unknowns.

A man weighs 170 lb on the surface of the earth. Compute his weight in an airplane flying at an elevation of 28 000 ft.

The cylindrical water tank with R = 10 ft and H = 1.6 ft has thin steel walls of uniform thickness and weighs 18000 lb when empty. Determine the depth of the water h for which the center of gravity G of the tank plus water will be located at the surface of the water. For water, use =62.4lb/ft3.

Calculate the resultant force caused by the water acting on the parabolic arch dam. The water levels are 16 ft on the upstream side and zero on the downstream side. For water, use =62.4lb/ft3.

The center of gravity of the nonhomogeneous bar AB is located at G. Find the angle at which the bar will be in equilibrium if it is free to slide on the frictionless cylindrical surface.

The parametric equations of the plane curve known as a cycloid are x=a(sin) and y=a(1cos). Use integration to find the coordinates of the centroid of the cycloid obtained by varying from 0 to 2 rad.

Repeat Prob. 4.152 assuming that the 400-kN force is applied at O instead of L.