## ksaimouli 2 years ago a compact disc has a radius of 6cm if the disc rotates about its central axis at a constant angular speed of 5 rev/s what is the total distance traveled by a point on the rim of the disc 40min

1. ksaimouli

when i did $\omega=\frac{ \theta }{ t }$

2. ksaimouli

3. ksaimouli

it did not work

4. Shane_B

This question doesn't even require physics...it's purely mathematical: First, calculate the circumference of the circle. Then multiply that by 5 since it makes 5 revolutions per second. That will give you how far the dot traveled in 1 second. Then just multiply that times how many seconds are in 40 minutes.

5. ksaimouli

Can u show me in physics way

6. Vincent-Lyon.Fr

$$\omega=\frac{ \theta }{ t }$$ is ok. You should just be careful to plug in the values in the right units.

7. ksaimouli

but @Vincent-Lyon.Fr i did not get the answer with this equation

8. Vincent-Lyon.Fr

Show us you numbers.

9. ksaimouli

$\theta=10\pi(2400)$

10. Vincent-Lyon.Fr

What the question asks is the DISTANCE travelled, not the angle swept during that time.

11. ksaimouli

Distance in rotation is nothing but the angle right?

12. Vincent-Lyon.Fr

No, distance is distance (in metres), and angle is angle (in radians).

13. ksaimouli

so i found theta so can i use s=r theta

14. ksaimouli

$s=r \theta$

15. Vincent-Lyon.Fr

Yep and you should find about 4.5 km