# Tangential and Normal of a rotating mass

1. Sep 30, 2016

### nysnacc

1. The problem statement, all variables and given/known data

2. Relevant equations
at = Rα
an = V2/ R = Rω2

Vt
Vn =0
3. The attempt at a solution
I found at=0
an=5.66 m/s
vt=3.364
vn=0

So v = vt = 3.364 m/s

Correct?

2. Sep 30, 2016

### haruspex

If you correct the units, yes.
Please show how you got that.

3. Sep 30, 2016

### nysnacc

oh yes, a in m/s^2 typo :)

for vt, first, I need ω, which is found from an = v^2/R where R is L sinθ

SO, v = sqrt (an*R) = sqrt (5.66*4sin30°) = 3.36 m/s

4. Sep 30, 2016

### Staff: Mentor

What are the units associated with that 4 (highlighted in red)?

5. Sep 30, 2016

### nysnacc

4 in meter, which is the length of L

6. Sep 30, 2016

### nysnacc

the question is modified, it was shown 4 ft but actually it should be in meter.

7. Sep 30, 2016

### Staff: Mentor

Ah. It would have been nice to have been made aware of this detail in the problem statement

In that case your tangential velocity looks okay.

8. Sep 30, 2016

### nysnacc

Hopefully I wouldn't make the same mistake next time, thanks for pointing out :)

And at = 0 (rotating in constant angular speed), vn = 0 (constant radius R) correct?

9. Sep 30, 2016

### Staff: Mentor

Yes.

10. Sep 30, 2016

### nysnacc

Great! Actually these questions appeared on my midterm today, and these were my answers