A right-angled cone (with base radius 5 cm and height 12 cm), as shown in fte figure below, is rolled on the ground keeping the point P fixed until the point Q (at the base of the cone, as shown) touches the ground again. By what angle (in radians) about P does the cone travel?
Correct Option : D
Base radius = 5cm, Height = 12 cm. So Slant Height = 13cm. If, we open it now then it appears as an arc with its radius = Slant Height of the cone = 13 cm. Length of the arc = Circumfernce of the cone = 2 × π × 5 = 10 π cm Now, when, length of arc is 2×p×13, angle subtended is 2π. So, angle subtended when length of arc is 10π = 2π/26π × 10π = 10π/13.