A cantilevered beam bracket of uniform cross section extends 12 inches from the wall and supports 100 pounds of load at the end with a safety factor of 5. To the nearest 0.1, what is the safety factor if the bracket is extended so that the load is now 18 inches from the wall and the load is changed to 72 pounds?
12 inches and 100 pounds gives you a moment of 1200 lb-inchs. With a safety factor of 5 the bracket must be able to support a torque of 6000 lb-inches. If you have a load suspended at 18 inches and 72 lbs, the torque is now 1296 lb-in. max strength of the bracket is still 6000 lb-inches therefore your new safety factor is 6000/1296 or 4.6296 or 4.6
