A girl is walking along a straight line at constant speed on a rotating platform, following a line painted onto the platform. She is walking with a speed of 1.7 m/s relative to the platform. The platform is rotating and goes around once every 30 seconds. When she is 5 m from the center of the platform what is the magnitude of her velocity relative to the ground (choose the closest answer in meters/sec – remember that her velocity relative to the platform is perpendicular to the velocity of the platform relative to the ground) — Solution here, velocity of girl relative to platforem , v1 = 1.7 m/s i the angular velocity of plateform , w = 2 * pi /T w = 2 * pi /30 = 0.21 rad/s velocity of r =5 m point , v2 = r * w = 1.05 m/s j the magnitude of her velocity relative to ground , v = sqrt(v1^2 + v2^2) v = 2 m/s .