Equations of motions, revolutions of turntable

[Jtappan]

Homework Statement

A turntable reaches an angular speed of 45.0 rpm, in 2.1 s, starting from rest.

(a) Assuming the angular acceleration is constant, what is its magnitude?
_2.24_rad/s2
(b) How many revolutions does the turntable make during this time interval?
______ rev

Homework Equations

The Attempt at a Solution

I am having trouble with the second part. I figured out magnitude of the angular acceleration but I don't remember how to find the revolutions. Anyone help?

 

[Bob Loblaw]

45RPM = 45 revolutions per minute. It seems that the question is asking you to find out how many revolutions the turntable makes in 2.1 seconds.

 

[Anadyne]

rpm stands for revolutions per minute right?

 

[Bob Loblaw]

rpm stands for revolutions per minute right?

Yes.

 

[Jtappan]

Yea RPM means revolutions per minute...but I broke it up into Rev/s and I still couldn't find the right answer. What do I do? any tips?

 

[learningphysics]

Yea RPM means revolutions per minute...but I broke it up into Rev/s and I still couldn't find the right answer. What do I do? any tips?

Think of angular velocity and acceleration, the same way as velocities when you do kinemtics problems.

For example in kinematics we have:

d = [(v1+v2)/2]*t

here we have:

angle traversed = [(w1 + w2)/2]*t

here w1 = 0. w2 is 45.0 rpm in rad/s. and you have time.

once you have the angle, you can get the number of revolutions.