A boy weighing 650 N wants to cross a creek by using a 5.00 meter long plank as a bridge. He places the plank across the creek and begins to walk across. Consider the supporting forces to be at the ends of the plank, and the plank itself to be weightless. At one point, the supporting force at the end where the boy is going is 250 N. Where is the boy located when this is the case?

Question

A boy weighing 650 N wants to cross a creek by using a 5.00 meter long plank as a bridge.  He places the plank across the creek and begins to walk across.  Consider the supporting forces to be at the ends of the plank, and the plank itself to be weightless.  At one point, the supporting force at the end where the boy is going is 250 N.  Where is the boy located when this is the case?

bobpursley · Answer

sum moments about the boy, located at x from the end where he is going. 250*x=(650-250)*(5-x) solve for x