$Assertion : $ Machine parts are jammed in winter.
$Reason :$ The viscosity of lubricant used in machine parts increase at low temperatures.
$Reason :$ The viscosity of lubricant used in machine parts increase at low temperatures.
AIIMS 2007, Easy
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Viscosity of a liquid decreases with increase in temperature and vice versa i.e, $\eta = \frac{1}{{\sqrt T }}$
$\therefore $ at low temperatures viscosity increases
$ \Rightarrow $ Viscous drag increases $F = - \eta A\frac{{dv}}{{dx}}$
$ \Rightarrow $ force required to move the body or machine increases hence, machines are fammed.
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