Answer:
The tangential velocity of a rotating object is:
v = r*w
where r is the radius, and w is the angular velocity.
w = 2*pi*f
where f is the frequency.
We know that the record plater does 11 revolutions in 20 seconds, then it does:
11 rev/20s = 0.55 rev/s = f
then we have:
w = 2*pi*0.55 s^-1 = 2*3.14*0.55 s^-1 = 3.454 s^-1
The radius of a record player is really variable, it is around 10 inches, so i will use r = 10in, which is the rotating part of the record player.
then the tangential velocity is:
v = 10in*3.454 s^-1 = 34.54 in/s