:surprised Okay, I first want to tell you that today is my birthday so if you want to doubley help me out, that would be great...(adsbygoogle = window.adsbygoogle || []).push({});

so i put my homework off because it was my homework weekend and now i'm screwed because i can't figure out these last two problems.

1.) A coin with a diameter of 2.40 cm is dropped on edge onto a horizontal surface. The coin starts out with an initial angular speed of 18 rad/s and rolls in a straight line without slipping. If the rotation slows with an angular accelerationb of magnitude 1.9rad/s^2, how far does the coin roll before coming to rest?

Answer: 1.2m

My work: chicken scratch-- I don't think I've done anything right. I know the radius is .012m and W initial is 18 rad/s and I think W final is 0, right? Alpha is 1.9rad/s^2 (or is this considered negative because it is slowing?) I have no idea what theta is, or the time.... I guess If I could solve for time, I'd be able to solve for theta, but I can't figure out how to solve for time seeing there is no theta distances. PLEASE HELP! I WANT TO CELEBRATE MY BIRTHDAY! : )

2.) A race car starts from rest on a circular track of radius 400 m. The car's speed increases at the constant rate of .500m/s^2. At the point where the magnitudes of the centripetal and tangential accelerations are equal, determine (a) the speed of the car, (b) the distance traveled, and (c) the elasped time.

I know a) Ac= v so .5=V^2/400 which gives v = 14.1 m/s

B) ???? I don't understand centripetal and tangential accelerations are equal??? I'm stuck here, so I'm obviously stuck for c.

Thanks to anyone who can help me out here....

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# Homework Help: Help for the Birthday Girl!

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