# Homework Help: Oscillator Questions

1. Jul 4, 2011

### wolves5

The position of the center of the box shown is given by the equation:
x = 4.4 m * cos(29/sec * t)

(a) What is the position of the box 2 seconds after the oscillations have started?
x = m
I dont know how to start A. I plugged in 2 seconds for t in the above equation, but my answer is not right.

(b) What is the amplitude of the box's oscillations?
The amplitude is 4.4 and it's correct.

(c) What is the period of the box's oscillations?
The period is 0.21666 seconds and its correct.

(d) What is the box's maximum velocity?
The max velocity is 127.6 m/s and its correct.

(e) What is the box's maximum acceleration?
The max acceleration si 3700.4 m/s2 and its correct.

(f) How long does it take the box to move from -2.2 m to +2.2 m?
I dont know how to approach this one either.

2. Jul 4, 2011

### lewando

What is "sec"?

3. Jul 4, 2011

seconds?

4. Jul 4, 2011

### lewando

What did you get for part a?

5. Jul 4, 2011

### wolves5

I did 4.4 * cos(29*2)= 2.33164. But this is not the right answer.

6. Jul 4, 2011

7. Jul 4, 2011

### wolves5

How do you do that when there's no units for the numerator? I tried doing 4.4 * cos (2pi/29 * 2), but that didnt work. How do you convert it?

8. Jul 4, 2011

### lewando

"29/sec" is most likely Hertz (cycles/sec). Need to convert this to rad/sec. 1 "cycle" = 2pi rad. So multiply 29 cycles/sec * 2pi rad/cycle.

9. Jul 4, 2011

### wolves5

Alright, when I converted it, my final answer was 4.386885896 and that is not right.

10. Jul 4, 2011

### lewando

I got 4.4 (3.999 considering SDs)

11. Jul 4, 2011

### wolves5

Its still not right. I don't understand any other way to solve for it.

12. Jul 4, 2011

### lewando

Is there anything special about "the box shown"? I am imagining a box attached to a device that makes it oscillate according to the described function. Does it start at x=0? EDIT: when t=0 where is the box?

13. Jul 4, 2011

### wolves5

I attached the picture. Can you see it? Its supposed to be an attachement.

#### Attached Files:

• ###### box.gif
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14. Jul 4, 2011

### Staff: Mentor

You might consider that 29*t/sec yields radians. No conversion required. What's 4.4m x cos(29 x 2 radians) ?

15. Jul 4, 2011

### wolves5

I got 2.331644763, which is also not correct.

16. Jul 4, 2011

### Staff: Mentor

That would be the result for 2*29 DEGREES. Try 2*29 RADIANS. Is your calculator set to degrees mode?

17. Jul 4, 2011

### lewando

So per equation, someone pulls the box out to the right to a 4.4m hash mark then lets go at t=0.

If 29 is in Hz, the result should be 4.4m
If 29 is in rad/sec, the result should be 0.52m (I dont think you checked this)