# Thread: Help with Trig. homework please

1. ## Help with Trig. homework please

I have recently started my first trig class and Im kind of lost on a couple of the homework problems. If a wheel has a central angle of 157.8 degrees and it rotates 150.5 times per second determine the radians/hour using angular velocity and miles/hour using linear velocity.

I dont even know what Im doing really. For the angular velocity problem I know in an hour it rotates 9030 times. I have to convert 157.8 degrees into radians and I did that and got 5.26pi/6. So Im not sure what to do next. I dont even know how to start the miles/hour problem. Can someone give me a hint please? Thanks.

2. Originally Posted by princesasabella
I have recently started my first trig class and Im kind of lost on a couple of the homework problems. If a wheel has a central angle of 157.8 degrees and it rotates 150.5 times per second determine the radians/hour using angular velocity and miles/hour using linear velocity.

I dont even know what Im doing really. For the angular velocity problem I know in an hour it rotates 9030 times. I have to convert 157.8 degrees into radians and I did that and got 5.26pi/6. So Im not sure what to do next. I dont even know how to start the miles/hour problem. Can someone give me a hint please? Thanks.
If the thing rotates $\frac{150.5}{s}$ this implies that $\omega=\frac{2(150.5)\pi{rad}}{s}$

Now the coversion to hours : $\frac{301\pi{rad}}{s}\cdot\frac{60s}{hr}=?$

Wouldn't we need te radius of the wheel to determine linear velocity?

3. Originally Posted by princesasabella
I have recently started my first trig class and Im kind of lost on a couple of the homework problems. If a wheel has a central angle of 157.8 degrees and it rotates 150.5 times per second determine the radians/hour using angular velocity and miles/hour using linear velocity.

I dont even know what Im doing really. For the angular velocity problem I know in an hour it rotates 9030 times. I have to convert 157.8 degrees into radians and I did that and got 5.26pi/6. So Im not sure what to do next. I dont even know how to start the miles/hour problem. Can someone give me a hint please? Thanks.
recheck the wording of the first problem. the 157.8 degree central angle has nothing to do with the problem, unless the corresponding arc length was given, so that you might find the wheel's radius (which you will need to find the linear velocity).

to convert revolutions per second to rad/hr ...

$\frac{rev}{sec} \cdot \frac{2\pi \, rad}{rev} \cdot \frac{3600 \, sec}{hr}$

the relationship between angular velocity, $\omega$ , and linear velocity , $v$ , is $v = r\omega$