A line AB 100mm long is a tangent at the top of a circular disc of 70mm diameter.The point A is at the top of the circumference.

The line AB rolls around thecircumference of the circle in a clockwise direction. Draw locus of point A until point Btouches the disc.

1 Answer

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Diameter of circle, ∅=70mm

AB = 100mm

Angle swept, $θ = \frac{AB}{Radius}= \frac{AB}{\frac{∅}{2}} = \frac{100}{35} rad$

∴ θ=163.7°

Length of each arc (1-2, 2-3, …) =$ \frac{Circumference}{No. \ of \ Divisions}= \frac{π∅}{8}= \frac{π× 70}{8} = 27.5mm$

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