Solving Rotational Motion Homework: Mass m, Length r, Centripetal Force Fc

[dixonewman]

Homework Statement

A rock of mass m=2kg is tied to a string of length r=4m is rotating at a constant rate and subject to a centripetal force Fc=32N.

Find the:
a)Centripetal acceleration

b)Angular velocity

c)Angular momentum

Homework Equations

a) Ac=V²_T/R (Fc=V²_T/R; so, V^2_T=Fc x R/m?)

b) V_T=angular velocity x radius

c) l = mv_Tr

The Attempt at a Solution

a) 32 x 4/2 = 64[m²/s]

b) V²_T = 64, so V_T = 8; 8/4 = 2 [rad/s]

c) 2 x 8 x 4= 64[kg x m²/s]

I know this is simple stuff, but I'm new to physics, and just wanted to double-check that I'm getting my formulas right. Thanks everyone!

 

[rock.freak667]

a) 32 x 4/2 = 64[m²/s]

Use Newton's 2nd law here.
[tex]F_{centripetal}=ma_{centripetal}[/tex]

b) V²_T = 64, so V_T = 8; 8/4 = 2 [rad/s]

This is correct. You could have also used [itex]F=m \omega^2r[/itex] if you wanted.

c) 2 x 8 x 4= 64[kg x m²/s]

[/QUOTE]

This looks good as well.

I know this is simple stuff, but I'm new to physics, and just wanted to double-check that I'm getting my formulas right. Thanks everyone![/QUOTE]

 

[dixonewman]

Wait, it looks like I may have jumbled up my formulas...

If V²_T=Fc x R/m (is this formula correct?), if so, then V²_T = 64;

Ac=V²_T/R so 64/4 = 16 [m/s²]

Am I still missing the mark?

 

[rock.freak667]

Wait, it looks like I may have jumbled up my formulas...

If V²_T=Fc x R/m (is this formula correct?), if so, then V²_T = 64;

Ac=V²_T/R so 64/4 = 16 [m/s²]

Am I still missing the mark?

16ms^-2 should be correct