Recent content by BillyCheung

Dear all A simple bridge made from uniform 6m long platform, whose centre of mass is at its midpoint. The mass of the bridge is 100kg. At one end A of the bridge, there is a frictionless hinge. A rope of negligible mass is attached to the other end B. This rope passes over a small...

Dear all I know that E(grav) = -GmM / r, Can I use Work done = F x s to calculate the P.E between two mass of the space? Thank a lot.Good Bye Billy

Dear all I know that torque = rxF, but I don't understand the concept of torque. Would you mind teach me? Thank a lot. Good Bye Billy

Last question, how do we calculate the magnitude of the horizontal component of the force exerted on the forearm by the rest of the arm when the foream is horizontal? Thank a lot.

Thank very much. The mass of the object is 2 kg. Good Bye

http://ccp.homeip.net/~billy/phy1.jpg Thank very much. In Figure 2, I think that 6 x cos 30 is correct answer. Why is your answer 6 x sin30? Thank a lot. Good Bye Billy

Dear all A simple bridge made from uniform 6m long platform, whose centre of mass is at its midpoint. The mass of the bridge is 100kg. At one end A of the bridge, there is a frictionless hinge. A rope of negligible mass is attached to the other end B. This rope passes over a small...

Thank very much. I understand your idea. On the other hand, the torque of this case should be (0.04m)(2kg)(9.8ms-2) = 0.784 Nm. Do you agree? And then what is the force exerted on the forearm by the rest of the arm at the elbow(pivot) if the forearm is stationary and in equilibrium...

Dear all : I have one question about tension that is following : The human forearm and hand can be modeled as a beam that is pivoted at one end(the elbow) and supported (by a muscle) at a short distance from the pivot. The beam(forearm) is horizontal, the muscle is vertical, the centre of...