7. Friction, Inclines, Systems

Two blocks are connected by a cord over a pulley. Block A rests on a rough tabletop. Block B has mass mB=2kg and hangs over the edge of the table. The coefficients of friction between Block A and the tabletop are μs=0.6 and μk=0.4. What is the minimum mass Block A can have to keep the system from starting to move?

(III) A small block of mass m rests on the rough, sloping side of a triangular block of mass M which itself rests on a horizontal frictionless table as shown in Fig. 5–44. If the coefficient of static friction is μ , determine the minimum horizontal force F applied to M that will cause the small block m to start moving up the incline. <IMAGE>

(II) In Fig. 5–36 the coefficient of static friction between mass m_A and the table is 0.40, whereas the coefficient of kinetic friction is 0.30.

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(b) What value(s) of m_A will keep the system moving at constant speed? [Ignore masses of the cord and the (frictionless) pulley.]

(III) A 4.0-kg block is stacked on top of a 12.0-kg block, which is accelerating along a horizontal table at a = 5.2m/s² (Fig. 5–43). Let μₖ = μₛ = μ .

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(a) What minimum coefficient of friction μ between the two blocks will prevent the 4.0-kg block from sliding off?

(III) A 4.0-kg block is stacked on top of a 12.0-kg block, which is accelerating along a horizontal table at a = 5.2m/s² (Fig. 5–43). Let μₖ = μₛ = μ .

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(b) If μ is only half this minimum value, what is the acceleration of the 4.0-kg block with respect to the table, and

(III) A 4.0-kg block is stacked on top of a 12.0-kg block, which is accelerating along a horizontal table at a = 5.2m/s² (Fig. 5–43). Let μₖ = μₛ = μ . <IMAGE>

(c) If μ is only half this minimum value, what is the acceleration of the 4.0-kg block with respect to the 12.0-kg block?