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Engineering Mechanics | polar co-ordinates problem

Q. The collar A in Figure slides along the rotating rod OB. The angular position  of the rod is given by πœƒ =2/3 *(πœ‹π‘‘)Β² rad and the distance of the collar from O varies as r =18t⁴+4 m, where time t is measured in seconds. Determine the velocity and acceleration vectors of the collar at t =0.4 s. Solution  :-     Given polar co-ordinates are      r = 18t⁴+4       and       πœƒ =2/3 Γ—(πœ‹π‘‘)Β²      r`= 72tΒ³                        πœƒ` =4/3 Γ—(πœ‹π‘‘)      r``= 216tΒ²                    πœƒ`` =4/3 Γ—(πœ‹) At t=0.4 sec       r = 18(0.4)⁴+4 = 4.46m       r`= 72(0.4)Β³ = 4.608 m/a       r``= 216(0.4)Β² = 34.56 m/sΒ²      πœƒ = 2Γ—(3.14Γ—0.4)Β²/3 =0.335 rad      πœƒ`= 4Γ—3.14Γ—0.4/3   = 1.675 rad/se...