parachutist attain if the retarding force of the parachute is proportional to the speed of descent?

8-2: ROTATIONAL EQUILIBRIUM

OBJECTIVE: Solve rigid-body problems by applying both the first and second conditions of equilibrium.
Commentary
Before spending a lot of time trying to solve a mechanical-equilibrium problem, you might want to find out whether a unique solution is in fact possible. To see if a unique solution is possible in a mechanical equilibrium problem, count the total number of unknown components of the forces acting on the system and compare this with the number of independent equations that may be derived fromSF = 0 and St_vect= 0; if there are more unknowns than there are equations relating them, then the equilibrium conditions alone are not sufficient to determine the solution.When you draw a free-body diagram and set up the equilibrium equations in preparation for solving a problem, it is more important to be thorough and consistent in identifying and labeling all forces than it is to correctly guess the direction of unknown forces. Note also that the coordinate system to which the torques are referred need not be the same as that to which the translational force components are referred.

5. Some physics teachers can be very devious. One such teacher drilled several holes in an otherwise good wooden meterstick and filled the holes with lead. He then gave the meterstick, a knife-edge fulcrum, and a hanging 0.100-kg mass to a student and asked him to find the mass and center of gravity of the modified meterstick. The student found that the stick balanced with the fulcrum at 0.58 m with the hanging mass at 0.66 m and also balanced at 0.73 m with the hanging mass at 0.93 m. Find the mass and the center of gravity.