A flexible drive belt runs over a frictionless pulley as shown in figure. The pulley is rotating freely about the vertical axis passing through the centre ‘O’ of the pulley. The vertical axis is fixed on the horizontal smooth surface. The mass per unit length of the drive belt is 1 kg/m and tension in the drive belt is 8N. The speed of the drive belt is 2m/s. Find the net normal force applied by the belt on the pulley in newton.
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answer is 8.
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Detailed Solution
Consider an element of mass dm=λRdθ at angle θ from reference.2Tsindθ2−dN=λRdθv2R(λ is linear mass density of belt )∴Tdθ−dN=λv2dθDue to symmetry , dNsinθ component will cancel out and dNcosθ adds up. ∴ So total normal = ∫-π2π2dNcosθ=∫-π2π2Tcosθdθ−λv2∫-π2π2cosθdθ⇒N=Tsinπ2--sinπ2-λv2sinπ2--sinπ2=2T-2λv2⇒N=2(8)-2(1)22=8N