Project ForgeConsider a slider crank mechanism with nonzero masses and inertia. A constant torque τ is applied on the crank as shown in the figure. Which of the following plots best resembles variation of crank angle, θ versus time? (A) a straight line through the origin (constant angular velocity); (B) a curve that rises then dips below zero, oscillating; (C) a smooth, ever-steepening exponential-like rise; (D) a generally rising curve with small periodic wiggles/undulations superimposed.
- Aa straight line through the origin (constant angular velocity)
- Ba curve that rises then dips below zero, oscillating
- Ca smooth, ever-steepening exponential-like rise
- a generally rising curve with small periodic wiggles/undulations superimposed
Explanation
With nonzero slider/connecting-rod mass and inertia, the resistance to a CONSTANT applied crank torque varies periodically over one revolution (since the inertia forces of the slider vary with crank angle). This causes the crank's angular velocity — and hence θ — to fluctuate periodically even as it steadily increases overall, producing a generally rising curve with small periodic undulations, exactly the kind of cyclic speed-fluctuation phenomenon flywheels are designed to smooth out.
Source: GATE ME 2015 (Session 1) (2015)
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