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In a wheel and axle, diameter of the wheel is 500 mm and that of the axle is 200 mm. The thickness of the cord on the wheel is 6 mm and that of the axle is 20 mm. Find the velocity ratio of the machine. If the efficiency when lifting a load of 1200 N with a velocity of 10 metres per minute is 70%, find the effort necessary. |
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Answer» Effective wheel diameter = \(\frac62\) + 500 + \(\frac62\) = 506 mm Effective axle diameter = \(\frac{20}2\) + 200 + \(\frac{20}2\) = 220 mm. For a wheel and axle, the velocity ratio is given by \(\frac Dd\) VR = \(\frac{506}{2.20}\)= 2.30 Mechanical advantage = Efficiency × velocity ratio = 0.7 × 2.30 = 1.61 MA = \(\frac WP\) p = \(\frac{1200}{1.61}\) P = 745.34 N |
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