Chapter 4, Problem 70P

The trapdoor is held in the horizontal plane by two wires. Replace the forces in the wires with an equivalent force R that passes through point A, and determine the y-coordinate of point A.

The trap door is held open by the rope AB. If the tension in the rope is T = 60 lb, determine its moment about the y-axis.

Find the moment about point A resulting from the force of the knee on the helmet, as shown. Also, find the force F at the base of the neck needed to resist this moment.

Draw the necessary free body diagrams.

The forces P and Q act on the handles of the wrench. If P = 321b and Q = 36 lb, determine the combined moment of the two forces about the z-axis.

The force F of magnitude 200 N is perpendicular to the plane ABC. Determine the magnitude of its moment about the x-axis.

Determine the magnitude of the moment of the 150-N force about point O. Also find the perpendicular distance between the line of action of the force and point O (as in M = Fd).

To lift the table without tilting, the combined moment of the four parallel forces must be zero about the x-axis and the y-axis (O is the center of the table). Determine the magnitude of the force F and the distance d.

Replace the three forces acting on the rectangular solid with a wrench. Specify the magnitude of the moment Massociated with the wrench. Enter a positive number for M if the wrench acts in a positive sense, enter a negative number if it acts in the negative sense. Specify the (x,y,z) coordinates of the point P in plane ABCD through which the line of action of the wrench passes. Illustrate the wrench moment and resultant in an appropriate sketch. 25 N 95 mm. Answers: M= y= 55 mm, 29 40 mm 20 N 110 mm. B N-m mm mm mm 35 mm 30 N