statics friction

Engineering Mechanics ( Statics ) : Friction

Dedicate Devoted ( Clear Math ) 086 – 323 – 3270 ( P Chai ) 1

The masses of the boxes are mA = 15 kg and mB = 60 kg. The coefficient of static friction between boxes A and B and between box B and the inclined surface is 0.12. What is the largest force F for which the boxes will not slip?

สนใจเรียนพิเศษติดต่อ 086 – 323 – 3270 ( พี่ชัย ) , 083 – 602 – 4008 ( พี่พงษ์ ) อยาก A อยาก B ต้อง * Clear Math* กลัว F ติด โปร นึกถึงเรา What is the smallest force F for which the boxes will not slip?



Determine whether the block shown is in equilibrium, and find the magnitude and direction of the friction force when θ = 30 o and P = 200 N.

สนใจเรียนพิเศษติดต่อ 086 – 323 – 3270 ( พี่ชัย ) , 083 – 602 – 4008 ( พี่พงษ์ )

อยาก A อยาก B ต้อง * Clear Math* กลัว F ติด โปร นึกถึงเรา



Considering only values of θ less than 90° , determine the smallest value of θ for which

motion of the block to the right is impending when (a ) m =30 kg, (b) m =40 kg.





A 19.5-ft ladder AB leans against a wall as shown. Assuming that the coefficient of static friction μs is the same at A and B, determine the smallest value of μs for which equilibrium is maintained.





A 19.5-ft ladder AB leans against a wall as shown. Assuming that the coefficient of static friction μs is

the same at A and B, determine the smallest value of μs for which equilibrium is maintained





The mass of the suspended object is 6 kg. The structure is supported at B by the normal and friction forces exerted on the plate by the wall. Neglect the weights of the bars. (a) What is the magnitude of the friction force exerted on the plate at B ? (b) What is the minimum coefficient of static friction at B necessary for the structure to remain in equilibrium?





Suppose that the lengths of the bars are LAB = 1.2 m and LAC = 1.0 m and their masses are mAB = 3.6 kg and mAC = 3.0 kg (a) What is the magnitude of the friction force exerted on the plate at B? (b) What is the minimum coefficient of static friction at B necessary for the structure to remain in equilibrium?





The 8 kg block A and the 16 kg block B are at rest on an incline as shown. Knowing that the coefficient of static friction is 0.25 between all surfaces of contact, determine the value of θ for which motion is impending.





The 10-lb metal disk A is at the center of the inclined surface. The tension in the string AB is 5 lb. What minimum coefficient of static friction between the disk and the surface is necessary to keep the disk from slipping?





The masses of crates A and B are 25 kg and 30 kg, respectively. The coefficient of static friction between the contacting surfaces is 0.34s . What is the largest value of for which the crates will remain in equilibrium?





The homogeneous semicylinder rests on a horizontal surface and is subjected to the force P applied to a cord firmly attached to its periphery. The force P is slowly increased and kept normal to the flat surface of the semicylinder. If slipping is observed just as reaches 40 , determine the coefficient of static friction and the value of P when slipping occurs





The horizontal bar is attached to a collar that slides on the smooth vertical bar. The collar at P slides on the smooth horizontal bar. The total mass of the horizontal bar and the two collars is 12 kg . The system is held in place by the pin in the circular slot. The pin contacts only the lower surface of the slot, and the coefficient of static friction between the pin and the slot is 0.8 If the system is in equilibrium and y = 260 mm, what is the magnitude of the friction force exerted on the pin by the slot?


What is the minimum height y at which the system can be in equilibrium?



Two blocks A and B have a weight of 10 lb and 6 lb, respectively. They are resting on the incline for which the coefficients of static friction are 0.15A and 0.25B . Determine the incline angle for which both blocks begin to slide. Also find the required stretch or compression in the connecting spring for this to occur. The spring has a stiffness of k = 2 lb/ft.




Two blocks A and B have a weight of 10 lb and 6 lb, respectively. They are resting on the incline for which the coefficients of static friction are 0.15A and 0.25B . Determine the angle which will cause motion of one of the blocks. What is the friction force under each of the blocks when this occurs? The spring has a stiffness of k = 2 lb/ft and is originally unstrectched.





The uniform 6 kg slender rod rests on the top center of the 3 kg block. If the coefficients of static friction at the points of contact are 0.4A , 0.6B and 0.3C , determine the largest couple moment M which can be applied to the largest couple moment which can be applied to the rod without causing motion of the rod.





A block of mass mO is placed between the vertical wall and the upper end A of the uniform slender bar of mass m. If the coefficient of static friction is

s between the block and the wall and also between the block and the bar, determine a general expression for the minimum value

min of for which the block will remain in equilibrium. Evaluate your expression for 0.5s and (a) 0.1

o

m

m , (b) 1

o

m

m and (c) 10

o

m

m For each case, state the minimum

coefficient of static friction s B necessary to prevent slippage at B




If the beam AD is loaded as shown, determine the horizontal force P which must be applied to the wedge in order to remove it from under the beam. The coefficients of static friction at the wedge’s top and bottom surfaces are 0.25CA and 0.35CB , respectively. If P = 0, is the wedge self – locking? Neglect the weight and size of the wedge and the thickness of the beam.




The coefficient of kinetic friction between the 40 kg crate and the slanting floor is

0.3k . If the angle 20 , what tension must the person exert on the rope to move the crate at constant speed?


อยาก A อยาก B ต้อง * Clear Math* กลัว F ติด โปร นึกถึงเรา For what angle is the tension necessary to move the crate at constant speed a minimum? What is the necessary tension?



Blocks A, B and C having the masses shown are at rest on an incline. Denoting by s the coefficient of static friction between all surfaces of contact, determine the smallest value of s for which equilibrium is maintained.





อยาก A อยาก B ต้อง * Clear Math* กลัว F ติด โปร นึกถึงเรา สนใจเรียนพิเศษติดต่อ 086 – 323 – 3270 ( พี่ชัย ) , 083 – 602 – 4008 ( พี่พงษ์ )



The 4.5 kg block A and the 3 kg block B are connected by a slender rod of negligible mass. The coefficient of static friction is 0.40 between all surfaces of contact. Knowing that for the position shown the rod is horizontal, determine the range of values of P for which equilibrium is maintained.





A slender steel rod of length 9 in. is placed inside a pipe as shown. Knowing that the coefficient of static friction between the rod and the pipe is 0.20, determine the largest value of θ for which the rod will not fall into the pipe.





Blocks A, B and D weight 75 lb and 30 lb, respectively. Using the coefficients of static friction indicated, determine the frictional force between blocks A and B and between block A and the floor C.





Blocks A and B have a mass of 7 kg and 10 kg, respectively. Using the coefficients of static friction indicated, determine the largest vertical force P which can be applied to the cord without causing motion.





A 16O wedge A of negligible mass is placed between two 80 kg blocks B and C which are at rest on inclined surfaces as shown. The coefficient of static friction is 0.40 between both the wedge and the blocks and block C and the incline. Determine the magnitude of the force P for which motion of the wedge is impending when the coefficient of static friction between block B and the incline is (a) 0.40 , (b) 0.60





อยาก A อยาก B ต้อง * Clear Math* กลัว F ติด โปร นึกถึงเรา สนใจเรียนพิเศษติดต่อ 086 – 323 – 3270 ( พี่ชัย ) , 083 – 602 – 4008 ( พี่พงษ์ )

statics friction

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