Telescopic boom and crane

The utility model discloses a telescopic lazy arm and a crane, the telescopic lazy arm comprises N sections of arms which are sequentially sleeved from outside to inside, and the telescopic lazy arm further comprises a telescopic arm winding drum, a telescopic arm winding drum, a telescopic arm rope, a telescopic arm rope and a lazy arm locking device; one end of the extending arm rope is wound on the extending arm winding drum, the other end of the extending arm rope is fixed at the root part of the Nth section of arm, and the extending arm rope sequentially bypasses the rope guider at the head part of the first section of arm and all rope guiders at the head parts and the root parts of the second section to the (N-1) th section of arm; one end of the arm retracting rope is wound on the arm retracting winding drum, and the other end is fixed on the Nth section of arm; and the suspension arm locking device is used for locking or unlocking the relative positions of the two adjacent sections of arms. The telesc