-F 750 mm F Mo 1.25 mm Prob. R4-4

A 10.0 m long ladder weighing 50.0 N rests against a smooth vertical wall. If the ladder is just on the verge of slipping when it makes a 50.0° angle with the ground find the coefficient of static friction between the ladder and ground. The ladder is in equilibrium. This means that the torque around ANY pivot point must be zero. In problems like this, you can pick the pivot point of your choice, and still solve for the correct forces. However, there is typically a choice for the pivot point that makes the problem solving steps possible or at least easier. This will depend on the problem, but often depends on the fact that the torque due to a force at the pivot point is zero. This lets you ignore those torque terms in your calculations. a. What is the best choice of pivot point for this problem? Select one: A. The base of the ladder B. The center of mass of the ladder C. The top of the ladder By selecting the base of the ladder, you can ignore the torque due to both the…

A war-wolf, or trebuchet, is a device used during the Middle Ages to throw rocks at castles and now sometimes used to fling pumpkins and pianos. A simple trebuchet is shown in the figure below. Model it as a stiff rod of negligible mass 3.00 m long and joining particles of mass m₁ = 0.120 kg and m₂ = 55.0 kg at its ends. It can turn on a frictionless horizontal axle perpendicular to the rod and 15.5 cm from the particle of larger mass. The rod is released from rest in a horizontal orientation. Find the maximum speed that the object of smaller mass attains when it leaves the trebuchet horizontally. m/s m₂ Need Help? Read It 3.00 m m₂ e

Force F = (8.55 N )î – (9.95 N )ê acts on a pebble with position vector T (6.87 m )ĵ – (2.53 m )k, relative to the origin. What is the resulting torque acting on the pebble about (a) the origin and (b) a point with coordinates (8.02 m, 0, - 6.52 m)?