A toy car rolls along a track, starting at the top of a ramp, then rolling down to floor level. After reaching the floor, the track contains a circular loop-the-loop with a diameter of 60 cm Calculate the minimum vertical height above the floor at which the car needs to start from rest, in order that it does not lose contact with the track when upside-down at the top of the loop. (Assume friction is negligible and g = 9.8 m/s.)