A block of mass 40 kg slides over a surface, when a mass of 4 kg is suspended through an inextensible massless string passing over frictionless pulley as shown below. The coefficient of kinetic friction between the surface and block is 0.02. The acceleration of block is (Given g=10 m s⁻².)

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(4) 8/(11) m s⁻². Idea: one system, two masses. The hanging weight drives it and friction under the sliding block resists. Driving force: m g=4×10=40 N. Friction, from the 40 kg block only — the hanging mass presses on nothing: f=μ Mg=0.02×40×10=8 N. Whole system, total mass 40+4=44 kg: a=(40-8)/(44)=(32)/(44)=8/(11) m s⁻². About 0.73 m s⁻² — small, because the 4 kg has to accelerate eleven times its own mass.

A block of mass 40 kg slides over a surface, when a mass of 4 kg is suspended through an inextensible massless string passing over frictionless pulley as shown below. The coefficient of kinetic friction between the surface and block is 0.02. The acceleration of block is (Given g=10 m s⁻².)

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