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1.10 Suppose that a particle moves around a circle in the plane , of radius r centered at 0, with constant speed v. Deduce from the previous exercise that y() and y"() are both orthogonal to y'(f), so it follows that y"(t) = k(t)y(r). Substitute this result into the equation obtained by differentiating y(t) y'(t) =0 to obtain k = - ?/r?. Thus the acceleration vector always points towards the origin and has constant length v3/r. article in $' with me