The velocity of the outside edge of the front sprocket can be obtained by using the basic equation for rotation about a fixed axis.
v1 = ω1 r1
But first, the given angular velocity needs to be converted to standard units.
ω1 = 60 rev/min = 6.28 rad/s
Substituting into the previous equation,
v1 = (6.28 rad/s)(120
mm) = 754 mm/s
The velocity v1 is relative to the center of the sprocket, which is moving with the bike. This will not affect the final answer since the rear sprocket is also moving with the bike.
Since the rear sprocket and front sprocket are connected by a chain, the tangential velocity of their edges will be the same
v1 = v2 (2)