Calculating Tangential Acceleration of an Astronaut in a Centrifuge

[pureouchies4717]

Astronauts use a centrifuge to simulate the acceleration of a rocket launch. The centrifuge takes 40.0 s to speed up from rest to its top speed of 1 rotation every 1.30 s. The astronaut is strapped into a seat 5.60 m from the axis.What is the astronaut's tangential acceleration during the first 40.0 s?

now, i know how to find a(c) and a(t) with mass, but they don't give mass in this problem

 

[pureouchies4717]

so here is what i have:

T= 1.3s
r= 5.6
tf= 40 s

 

[pureouchies4717]

if i had mass, i could just plug it into T=(mv^2)/r

v would be easy to find

 

[pureouchies4717]

ahhhhh 45 minutes. any help would be appreciated