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

Question

ksaimouli · Answer

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

ksaimouli · Answer

but why? (ur answer)

ksaimouli · Answer

it did not work

shane_b · Answer

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.

ksaimouli · Answer

Can u show me in physics way

vincent-lyon.fr · Answer

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

ksaimouli · Answer

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

vincent-lyon.fr · Answer

Show us you numbers.

ksaimouli · Answer

$$\theta=10\pi(2400)$$

vincent-lyon.fr · Answer

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

ksaimouli · Answer

Distance in rotation is nothing but the angle right?

vincent-lyon.fr · Answer

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

ksaimouli · Answer

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

ksaimouli · Answer

$$s=r \theta$$

vincent-lyon.fr · Answer

Yep and you should find about 4.5 km