Knocking Over a Post. One end of a post weighing 400 N and with height h rests on a rough horizontal surface with μs = 0.30. The upper end is held by a rope fastened to the surface and making an angle of 36.9° with the post ( Fig. P11.90 ). A horizontal force F → is exerted on the post as shown, (a) If the force F → is applied at the midpoint of the post, what is the largest value it can have without causing the post to slip? (b) How large can the force be without causing the post to slip if its point of application is 6 10 of the way from the ground to the top of the post? (c) Show that if the point of application of the force is too high, the post cannot be made to slip, no matter how great the force. Find the critical height for the point of application.
Knocking Over a Post. One end of a post weighing 400 N and with height h rests on a rough horizontal surface with μs = 0.30. The upper end is held by a rope fastened to the surface and making an angle of 36.9° with the post ( Fig. P11.90 ). A horizontal force F → is exerted on the post as shown, (a) If the force F → is applied at the midpoint of the post, what is the largest value it can have without causing the post to slip? (b) How large can the force be without causing the post to slip if its point of application is 6 10 of the way from the ground to the top of the post? (c) Show that if the point of application of the force is too high, the post cannot be made to slip, no matter how great the force. Find the critical height for the point of application.
Knocking Over a Post. One end of a post weighing 400 N and with height h rests on a rough horizontal surface with μs = 0.30. The upper end is held by a rope fastened to the surface and making an angle of 36.9° with the post (Fig. P11.90). A horizontal force
F
→
is exerted on the post as shown, (a) If the force
F
→
is applied at the midpoint of the post, what is the largest value it can have without causing the post to slip? (b) How large can the force be without causing the post to slip if its point of application is
6
10
of the way from the ground to the top of the post? (c) Show that if the point of application of the force is too high, the post cannot be made to slip, no matter how great the force. Find the critical height for the point of application.
Chapter 12, Problem 028 GO
In the figure, suppose the length L of the uniform bar is 2.7 m and its weight is 220 N. Also, let the block's weight W = 280 N and the angle 0 = 27°. The wire can withstand a maximum tension of
440 N. (a) What is the maximum possible distance x before the wire breaks? With the block placed at this maximum x, what are the (b) horizontal and (c) vertical
components of the force on the bar from the hinge at A?
com
A
(a) Number
Units
(b) Number
Units
(c) Number
Units
Click if you would like to Show Work for this question: Open Show Work
In the figure, a lead brick rests horizontally on cylinders A and B. The areas of the top faces of the cylinders are related by A4= 2.8 Ag;
the Young's moduli of the cylinders are related by Ea= 2.3 Eg. The cylinders had identical lengths before the brick was placed on them.
What fraction of the brick's mass is supported (a) by cylinder A and (b) by cylinder B? The horizontal distances between the center of
mass of the brick and the centerlines of the cylinders are dafor cylinder A and d; for cylinder B. (c) What is the ratio da/dg?
com of brick
A
(a) Number
i
Units
(b) Number
i
Units
(c) Number
i
Units
One end of a uniform ℓ = 4.70-m-long rod of weight w is supported by a cable at an angle of ? = 37° with the rod. The other end rests against a wall, where it is held by friction (see figure). The coefficient of static friction between the wall and the rod is ?s = 0.520. Determine the minimum distance x from point A at which an additional weight w (the same as the weight of the rod) can be hung without causing the rod to slip at point A.
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