Angle does it rotate & angular acceleration?

[DrMcDreamy]

Homework Statement

This is a two part problem, but I don't know what equation to use for part II.

a) A record has an angular speed of 15.4 rev/min. What is its angular speed? Answer in units of rad/s. 1.61 rad/s

b) Through what angle does it rotate in 1.1 s? Answer in units of rad.

Homework Equations

What equation am I supposed to use?

...

Homework Statement

A wheel rotating with a constant angular acceleration turns through 11 revolutions during a 6 s time interval. Its angular velocity at the end of this interval is 17 rad/s. What is the angular acceleration of the wheel? Note that the initial angular velocity is not zero. Answer in units of rad/s2.

Homework Equations

What equation am I supposed to use?

 

[232Thorium]

Just like linear kinematics but for rotations.

Linear: position = x, speed = v
Angular: position = $$\theta$$, speed = $$\omega$$

So for linear, you know x=x₀+vt. Write out the similar equation for rotation and it will give you your angle in radians.

...

Same concept as before: substitute angular variables for linear ones in linear kinematics equations.

Known: $$\Delta\theta, t, \omega_f$$
Want: $$\alpha$$
Need: $$\omega_0$$ to get $$\alpha$$

Work it out in two steps, first one gets you $$\omega_0$$ in terms of $$\alpha$$, plug that into another equation that relates $$\Delta\theta$$ to the everything you know so far and then solve for $$\alpha$$.

 

[PhanthomJay]

Homework Statement

This is a two part problem, but I don't know what equation to use for part II.

a) A record has an angular speed of 15.4 rev/min. What is its angular speed? Answer in units of rad/s. 1.61 rad/s

b) Through what angle does it rotate in 1.1 s? Answer in units of rad.

Homework Equations

What equation am I supposed to use?

you are going to have use the appropriate angular motion equation

...

Homework Statement

A wheel rotating with a constant angular acceleration turns through 11 revolutions during a 6 s time interval. Its angular velocity at the end of this interval is 17 rad/s. What is the angular acceleration of the wheel? Note that the initial angular velocity is not zero. Answer in units of rad/s2.

Homework Equations

What equation am I supposed to use?

What is the angular motion equation that relates angular displacement with angular acceleration and time?

 

[DrMcDreamy]

Through what angle does it rotate in 1.1 s? Answer in units of rad.

So it would be: $$\omega$$ = $$\omega$$ _o + $$\alpha$$ t

What is the angular acceleration of the wheel? Note that the initial angular velocity is not zero. Answer in units of rad/s2.

$$\omega$$ = $$\omega$$ _o + $$\alpha$$ t

than:

$$\alpha$$ = $$\Delta$$ $$\omega$$ / $$\Delta$$ t

 

[PhanthomJay]

There are several motion equations to choose from, and which one you use depends upon the problem. In part 1, you have a constant angular speed, and the time is given. You don't have any acceleration, it's a record spinning at a uniform angular speed. In part 2, follow 232thorium's hint.