Question1

In a “Rotor-ride” at a carnival, people rotate in a vertical cylindrically walled “room.” If the room radius was 5.5 m, and the rotation frequency 0.50 revolutions per second when the floor drops out, what minimum coefficient of static friction keeps the people from slipping down? People on this ride said they were “pressed against the wall.” Is there actually an outward force pressing them against the wall? If so, what is its source? If not, what is the proper description of their situation (besides nausea)?

Question2

What is current temperature and peak wavelength of the cosmic microwave background (CMB)? Knowing that peak wavelength scales as the inverse of (1+z) where z is the redshift, even as the temperature scales as (1 + z), compute the peak wavelength and temperature at matter-radiation decoupling (z ' 1000).Will most of CMB photons, at the time of decoupling, have enough energy to ionize hydrogen atoms? So does it make sense to you that scientists say that the Universe "recombine" at this redshift (that means electrons "attach" to protons to form neutral hydrogen)?