Q. A professor's office door is 0.95 m wide, 2 m high and 4.0cm thick; has a mass of 25 kg; and pivots on frictionless hinges. A "door closer" is attached to the door and the top of the door frame. When the door is open and at rest, the door closer exerts a torque of 5.40 NxM. What is the least force that you need to be relevant to the door to hold it open?
Q. A man can row a boat at a speed of 5.95km/h in still water. If he is crossing a river where the current is 1.25km/h, in what direction must his boat be headed if he wants to reach a point directly opposite his starting point?