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EMech Prob Set IV Friction

This document contains 12 mechanics problems related to friction forces. The problems involve blocks on inclined planes, cylinders resting on surfaces, poles being supported, wheels on surfaces, and wedges being used to adjust columns. Friction forces and minimum forces required to initiate motion are calculated for each system. Coefficients of static and kinetic friction are provided, ranging from 0.2 to 0.4. Solutions involve determining friction forces, minimum initiating forces, and the range of applied forces or weights that will maintain equilibrium.

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Samrat Sadhukhan
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76 views3 pages

EMech Prob Set IV Friction

This document contains 12 mechanics problems related to friction forces. The problems involve blocks on inclined planes, cylinders resting on surfaces, poles being supported, wheels on surfaces, and wedges being used to adjust columns. Friction forces and minimum forces required to initiate motion are calculated for each system. Coefficients of static and kinetic friction are provided, ranging from 0.2 to 0.4. Solutions involve determining friction forces, minimum initiating forces, and the range of applied forces or weights that will maintain equilibrium.

Uploaded by

Samrat Sadhukhan
Copyright
© © All Rights Reserved
Available Formats
Download as PDF, TXT or read online on Scribd
Download as pdf or txt
Download as pdf or txt
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Engineering Mechanics

Jadavpur University

Prob. Set (IV) Friction

1. The coefficients of static and kinetic friction between the 100 kg block and the inclined plane are 0.30 and 0.20,
respectively. Determine (a) the friction force F acting on the block when P is applied with a magnitude of 200 N to the
block at rest, (b) the force P required to initiate motion up the incline from rest, and (c) the friction force F acting on the
block if P=600 N. [65.96 N, 516.33 N, 148.5 N]

2. The magnitude of force P is slowly increased. Does the homogeneous box of mass m slip or tip first? State the value
of P which would cause each occurrence. Neglect any effect of the size of the small feet. [slip, 0.448mg, 0.536mg]

3. The light bar is used to support the 50 kg block in its vertical guides. If the coefficient of static friction is 0.30 at the
upper end of the bar and 0.40 at the lower end of the bar, find the friction force acting at each end for x=75 mm. Also
find the maximum value of x for which the bar will not slip. (126.6 N at each end, 86.2 mm)
4. The 30kg homogeneous cylinder of 400 mm diameter rests against the vertical and inclined surfaces as shown. If the
coefficient of static friction between the cylinder and the surface is 0.30, calculate the applied clockwise couple M which
would cause the cylinder to slip. [32.9 N-m]

5. The uniform 7 m pole weighs 100 kg and is supported as shown. Calculate the force P required to move the pole if the
coefficient of static friction for each contact location is 0.40. (775 N)

6. The strut AB of negligible mass is hinged to the horizontal surface at A and to the uniform 25-kg wheel at B.
Determine the minimum couple M applied to the wheel which will cause it to slip if the coefficient of static friction
between the wheel and the surface is 0.40. [19.81 N-m]

7. The system of two blocks, cable, and fixed pulley is initially at rest. Determine the horizontal force P necessary to
cause motion when (a) P is applied to the 5 kg block and (b) P is applied to the 10 kg block. Determine the
corresponding tension T in the cable for each case. ((a) 137.3 N, 112.8 N; (b) 137.3 N, 24.5 N)
8. Determine the range of weights W for which the 100 kg block is in equilibrium. All wheels and pulleys have
negligible friction. (min. 3.05 kg, max. 31.7 kg)

9. The coefficient of static friction between the 100 kg body and the 150 wedge is 0.20. Determine the magnitude of the
force P required to raise the 100 kg body if (a) rollers of negligible friction are present under the wedge, and (b) the
rollers are removed and the coefficient of static friction applies at this surface as well. [485 N, 681 N]

10. For the previous problem, for both conditions (a) and (b), determine the magnitude and direction of the force P ‘ to
lower the 100 kg body. [63.3 N left, 132.9 right]

11. The two 50 wedges shown are used to adjust the position of the column under a vertical load of 5 kN. Determine the
magnitude of the forces required to raise the column if the coefficient of friction for all surfaces is 0.40. [4.53 kN]

12. For the previous problem, if the column is to be lowered, calculate the horizontal forces P’ required to with-draw the
wedges. [3.51 kN]

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