The prime circle of a cam is

A.The smallest circle drawn to the pitch curve from the centre of rotation of curve
B.The smallest circle drawn to the cam profile from the centre of rotation of a radial cam
C.The circle with centre as the centre of cam axis and radius such that it passes through the pitch point
D.The circle fitting in cam profile
E.None of the above

At critical speed

A.The shaforuns smoothly
B.The shaft runs with noise due to vibrations
C.The shaft becomes dynamically unstable with negligible lateral amplitudes
D.The shaft becomes dynamically unstable with large lateral amplitudes
E.None of the above