Answer:
vc = v cannon
mc = m cannon
vb = v ball
mb = m ball
vc = d / t
= (6.1 cm) / (0.0218 s)
= 280 cm/s
mb x vb = -mc x vc
(negative as it is in the opposite direction)
(0.0562) x vb = - (1.27) x (-280)
vb = - (1.27) x (-280) / (0.0562)
= 6323.26 cm/s
ball = 63.2 m/s
cannon = 2.8 cm/s - recommend changing to m before calculations