A thin uniform conducting disc of radius r and mass m rests on a horizontal tabletop where a uniform magnetic field of induction B nointing vertically upwards exists. Coefficient of friction between the disc and the tabletop is u. Two points P, and P, on the rim of the disc are connected with two flexible wires, which facilitate a current to flow through the disc. The contact points P1 and P2 subtend an angle 0 at the centre of the disc. How much minimum current must flow through the disc so that it begins to slide? Acceleration of free fall is g. s: umg B P2 P1 I

A thin uniform conducting disc of radius r and mass m rests on a horizontal tabletop where a uniform magnetic field of induction B nointing vertically upwards exists. Coefficient of friction between the disc and the tabletop is u. Two points P, and P, on the rim of the disc are connected with two flexible wires, which facilitate a current to flow through the disc. The contact points P1 and P2 subtend an angle 0 at the centre of the disc. How much minimum current must flow through the disc so that it begins to slide? Acceleration of free fall is g. s: umg B P2 P1 I

International Edition---engineering Mechanics: Statics, 4th Edition

4th Edition

ISBN:9781305501607

Author:Andrew Pytel And Jaan Kiusalaas

Publisher:Andrew Pytel And Jaan Kiusalaas

Chapter7: Dry Friction

Section: Chapter Questions

Problem 7.36P: The coeffient of static friction between the uniform bar AB of weight W and the ground is 0.45. Find...

See similar textbooks

Similar questions

Problem#2: Form the figure shown, a flexible belt placed around a rotating drum of 4-inch radius acts as a brake when the arm ABCD is pulled down by the force P. The coefficient of kinetic friction between the belt and the drum is 0.7. What force P that would result in a braking torque of 400 lb. in., assuming that the drum is rotating counterclockwise. Neglect the weight of the brake arm. 60° A 2 in.- B 4 in. 60° 24-2in1- -2 in. D Р
Figure 1 shows a railroad wagon axle and forces acting over it. There are two disc brakes on the wagon axle. Since the wagon wheels are not driven wheels, the load bearing element to which the wheels are connected is called axles. The axle is supported at both ends with bearing A and bearing B and the the weight of the wagon (G) is evenly distributed on both bearings (as G/2). During braking, two disc brakes on the axle are applied Ff force and Ft friction forces are formed on the wheels. Therefore the axle is forced to bend in the vertical direction with the effect of wagon weight (G) and wheel reaction forces (Rt), and in horizontal direction with the effect of braking (Ff) and wheel friction (Ft) forces. At the same time, the axle is forced under torsion because of Ff and Ft forces. GIVEN:Shaft material : 50CrMo4 Wheel material : GS 60 Brake discs’s material: 15Cr3 All the radiuses : 5 mm Average roughnesses for press fit surfaces: Ra =6.3 μm Wheel speed: = 500 d/d Wagon weight per…
two cylinders are connected to form a parallel cylinder actuatingsystem. Assume the bore and rod diameters of the left cylinder are 120 mm and 60 mm, respectively, and that those of the right cylinder are 100 mm and 50 mm. If the mass of the external loads to be driven by the left and right cylinders are 750 and 500 kg, respectively, and the back pressure in both rod-end chambers is 200 kPa, calculate the operating pressure of each cylinder for driving the loads. (Assume that the left cylinder requires 550 kPa for no-load extension and the right one requires 500 kPa.) If the supplying flow is 150 L ・ min−1, what are the extending velocities of those cylinders? Consider the friction and back pressure for the design Will those two cylinders extend simultaneously under the stated condition
A uniform circular disk, of 6-kg mass and 0.4-m radius, is placed at the corner, in contact with a vertical wall at A and a horizontal floor at B (Figure 6). A 100-N force is applied to the disk at the top point in the direction as shown in the figure. It is known that the coefficients of static friction between the disk and the wall and the floor are the same. question : Set up three equations of equilibrium at the critical state just about to move, in terms of thenormal forces (NA, NB) and the coefficient of static friction.
4. The system on the right consists of three solid circular cross-section rods 1, 2 and 3. All are made from the same material with a Young's modulus of E. Forces 2P and P act at connectors C and D. Assume that as the system deforms, the connectors C and D are allowed to translate but not rotate. Assume the weight of the rods is small compared to the loads and can therefore be neglected. 1. Is this system determinate or indeterminate? 2. Write down the equilibrium force and momentum equations for connectors C and D hint: draw the FBD for C and D 3. Write the elongation equations relating the elongations to axial loads for each the three rods. 4. Write down the compatibility equations relating the elemental elongations in the rod system. 5. Solve for the axial loads in each element. State whether each element is in tension or compression. 2d (3) 3L 2P P D L 2L (2) 4d C (1) 4d B
Form the figure shown, a flexible belt placed around a rotating drum of 4-inch radius acts as a brake when the arm ABCD is pulled down by the force P. The coefficient of kinetic friction between the belt and the drum is 0.7. What force P that would result in a braking torque of 400 lb . in., assuming that the drum is rotating Neglect the weight of the counterclockwise. brake arm. 60° 4 in. 60° A B C -2 in.²4in. 2 in. 42×-| -2 D P
What is the ratio L/R for which the uniform wire figure can be balanced in the position shown?
The coeffient of static friction between the uniform bar AB of weight W and the ground is 0.45. Find the smallest angle and the corresponding force P that would initiate simultaneous tipping and sliding of the bar.
The figure below shows a cylinder, which is rotating in clockwise direction. A lever is pushing onto the cylinder, thus exerting a braking torque. The lever itself is loaded by a force FE . a) Draw the free-body diagram of the lever, determine the direction of the kinetic friction force.
The diameter of two pulleys are (0.3m)and (0.2m), center distance (1m).if we use open belt drive. Determine: 1- the length of V- belt (2ß = 60°). 2- the contact angle between belt and smaller pulley. 3- the horse power, if the smaller pulley turn with speed (400r.p.m) and the tension force in tight side (T1=90ON), coefficient of friction u=0.3 4- the speed of large pulley.
1. A uniform ladder of mass m and length is leaning at rest against a wall at an angle 0. The coefficient of static friction between the floor and the ladder is μ5₁, and that between the wall and the ladder is Ms2. (a) Draw an FBD of the ladder when it is at rest. (b) Find out the measure of in terms of usi and μs2. (Hint: Consider torque and rotational equilibrium) (c) What is the trajectory, i.e., path of motion, of the center of the ladder as it slides down? (d) Given that the instantaneous speed of the top of the ladder is VÀ at some moment as it slides down, what are the speeds of the other end and the center of the ladder at the same moment? A 2. A ring with mass m is attached to a string. The string holds a block M as well through a pulley system. m is moving downward with an acceleration a' relative to the string. What is the friction between the ring m and the string in terms of g? The pulley and string are both ideal. mo M
Problem#3: For the figure shown, two blocks are connected by a uniform solid rod attached to each block with frictionless pins. If the coefficient of friction under each block is 0.65 and B weighs 2700 N, find the minimum weight of A to prevent motion. A 30° 60°