Chapter 8, Problem 23P

4. The mine car and its contents have a total mass of 6000 kg and a centre of gravity at G. If the coefficient of static friction 10 kN between the wheels and the 0.9 m •G tracks is u = 0.4 when the wheels are locked, find the normal force acting on the front wheels at B and the rear 0.15 m 0.6 m - 1.5 m wheels at A when the brakes at both A and B are locked. Does the car move? [Ans. NA = 16.5 kN, Ng =42.3 kN, the car does not move] %3D lyp

The 113-lb force P is applied to the 250-lb crate, which is stationary before the force is applied. Determine the magnitude and direction of the friction force F exerted by the horizontal surface on the crate. The friction force is positive if to the right, negative if to the left. Assume μ = 0.41, μ = 0.32. P Answer: F = i H lb

The 111-lb force Pis applied to the 230-lb crate, which is stationary before the force is applied. Determine the magnitude and direction of the friction force Fexerted by the horizontal surface on the crate. The friction force is positive if to the right, negative if to the left. Assume u, = 0.47, µ = 0.39. P Answer: F = i Ib

The uniform box shown in next figure, has a mass of 40 Kg. If the two forces T 60 N and F 30 N are applied on the box, determine if it remains in equilibrium. The coefficient of static friction (u) = 0.24 F=30N T=60N 30 40 Kg

The coefficients of static and kinetic friction between the drum and brake bar are μS= 0.4 and μK= 0.3, respectively. If M= 50 N.m and P= 85 N. determine the horizontal and vertical components of reaction at the pin O (shown in Fig. 3). Neglect the weight and thickness of the brake. The drum has a mass of 25 kg.

The 76-lb force P is applied to the 180-lb crate, which is stationary before the force is applied. Determine the magnitude and direction of the friction force F exerted by the horizontal surface on the crate. The friction force is positive if to the right, negative if to the left. Assume Ms = 0.43, Mk = 0.35. P Answer: F = i lb

4. The three bars have a weight of WA = 20 lb, WB = 40 lb, and We = 60 lb, respectively. If the coefficients of static friction at the surfaces of contact are as shown, determine the smallest horizontal force P needed to move block A CCB=0.5 BR 0.3 AHAD 0.2 D P

B: A roll of paper has a uniform weight of 2kN and is suspended from the wire hanger so that it rests against the wall. If the hanger has a negligible weight and the bearing at 0 can be considered frictionless, determine the force P needed to start turning the roll if 6 = 30°. The coefficient of static friction between the wall and the paper is µ, = 0.3. 12 cm

The rope running over two fixed cylinders carries the 4-kg mass at one end. Determine the force P that must be applied to the other end to initiate motion. The coefficient of static friction between the rope and the cylinders is 0.15. 50 mm 150 mm 400 mm 4 kg O 64.1 N 63.1 N 65.1 N O 62.1 N