Calculating Revolutions for a Spinning Wheel | Circular Motion Problem

[DTK]

Homework Statement

A wheel spins at an angular speed of 2.50 rad/s for a total of 30.0s. How many complete revolutions will the wheel make during this time?
A) 31.4 rev
B) 19.3 rev
C) 11.9 rev
D) 75.0 rev

Homework Equations

W=Wo+(alpha)(t)
θ=θo+Wot+1/2(alpha)t^2
W^2=Wo^2+2(alpha)(θ-θo)

The Attempt at a Solution

W=Wo+(alpha)t
2.5rad/s=(alpha)(30s)
Alpha=0.083

W^2=Wo^2+2(alpha)(θ-θo)
(2.5)^2=2(0.083)θ
37.6=θ

The answer I got doesn't match any of the possible answers on my worksheet so I know I'm doing something totally wrong. Please help me out this seemed pretty simple but I got stuck.

 

[Chestermiller]

What fraction of a circle is 2.5 radians?

 

[SammyS]

Homework Statement

A wheel spins at an angular speed of 2.50 rad/s for a total of 30.0s. How many complete revolutions will the wheel make during this time?
A) 31.4 rev
B) 19.3 rev
C) 11.9 rev
D) 75.0 rev

Homework Equations

W=Wo+(alpha)(t)
θ=θo+Wot+1/2(alpha)t^2
W^2=Wo^2+2(alpha)(θ-θo)

The Attempt at a Solution

W=Wo+(alpha)t
2.5rad/s=(alpha)(30s)
Alpha=0.083

W^2=Wo^2+2(alpha)(θ-θo)
(2.5)^2=2(0.083)θ
37.6=θ

The answer I got doesn't match any of the possible answers on my worksheet so I know I'm doing something totally wrong. Please help me out this seemed pretty simple but I got stuck.

There is nothing said about acceleration.

The wheel is rotating at a constant angular (rotational) speed.

 

[theodoros.mihos]

How many complete revolutions will the wheel make during this time?

 

[DTK]

What fraction of a circle is 2.5 radians?

I have no idea.

 

[Chestermiller]

I have no idea.

How many degrees is 2.5 radians?

 

[DTK]

How many degrees is 2.5 radians?

I got 37.6=θ is that what you are asking?

 

[Chestermiller]

I got 37.6=θ is that what you are asking?

2.5 radians is much more than that.

 

[DTK]

2.5 radians is much more than that.

Okay how do you work it out? I obviously did it wrong. How do I get the right answer to the question

 

[Chestermiller]

Okay how do you work it out? I obviously did it wrong. How do I get the right answer to the question

Do you know how to convert radians to degrees or to revolutions?

 

[DTK]

Do you know how to convert radians to degrees or to revolutions?

No

 

[Chestermiller]

No

Then you are not going to be able to do this problem until you do know. So go look it up in your math book or google radian.

 

[DTK]

Then you are not going to be able to do this problem until you do know. So go look it up in your math book or google radian.

2.5 radian equals 143.239 degree according to google

 

[Chestermiller]

2.5 radian equals 143.239 degree according to google

How many degrees are the in one revolution?

 

[DTK]

How many degrees are the in one revolution?

1 revoltuon equals 360 degrees. 1 degree equals 0.00277 revolutions

 

[Chestermiller]

1 revoltuon equals 360 degrees. 1 degree equals 0.00277 revolutions

Excellent. So, based on this, how many revolutions is 143.239 degrees?

 

[DTK]

Excellent. So, based on this, how many revolutions is 143.239 degrees?

0.3978

 

[Chestermiller]

0.3978

Excellent again. So it's rotating 0.3978 revolutions every second . How many revolutions does it rotate in 30 sec

 

[DTK]

Excellent again. So it's rotating 0.3978 revolutions every second . How many revolutions does it rotate in 30 sec

11.9 thank you