An air conditioning unit is vibrating in simple harmonic motion ...

[LaDunn]

An air conditioning unit is vibrating in simple harmonic motion with a period of 0.27 s and a range (from the maximum in one direction to the maximum in the other) of 3.0 cm. At t = 0 it is at its central position and moving in the +x direction.
 
  What is its position when t = 55 s? A)
 
  x = -0.430 cm
  B)
 
  x = -0.511 cm
  C)
 
  x = 0.511 cm
  D)
 
  x = -1.41 cm
  E)
 
  x = -1.44 cm

Question 2

A grinding wheel is spinning at a rate of 20.0 revolutions per second.
 
  When the power to the grinder is turned off, the grinding wheel slows with constant angular acceleration and takes 80.0 s to come to a rest.
  (a) What was the angular acceleration of the grinding wheel as it came to rest?
  (b) How many rotations did the wheel make during the time it was coming to rest?

[xiaomengxian]

Answer to Question 1

E

Answer to Question 2

(a) 1.57 rad/s2
(b) 800 revolutions

[LaDunn]

Excellent

[olderstudent]

Wow, this really help