Is it possible to have a platonic relationship when there is mutual physical attraction?

That's iffy. Usually not. If one person is & the other person isn't then sometimes it still works. Case in point me & best friend. He always wanted more, I never did. We're still best friends after 20+yrs. But if you are BOTH attracted to each other . . . I don't know about that. I think it would be too difficult to keep it as strictly friendship. It's playing with fire really.