A tuning fork vibrates 240 times per second. What is the frequency and period?

Frequency is expressed in Hertz, which is simply cycles per second. If a tuning fork (or anything else, for that matter) vibrates 1 time each second, it's frequency is 1 Hz. So then, if it vibrates 4280 in 20 seconds, then 4280÷20=214 cycles per second = 214 Hz.

c because the action was the roller coaster reaches bottom of hill (action) reaction would be blood tends to drain away from head

hope this !

54 degrees incident angle = reflected angle

angle is from normal turned to line of ray