Recent content by kplooksafterme

Homework Statement Consider the solid S described below. The base of S is the region enclosed by the parabola y = 5 - 2x2 and the x-axis. Cross-sections perpendicular to the y-axis are squares. Find the volume V of this solid. Homework Equations The Attempt at a Solution I know...

Thanks a lot for your help btw...

I think I also confused the rotational velocity of the ball with the rotational velocity of the ball moving around the cylinder. So the rotational velocity given in this question refers to the ball rotating about its own center of mass rather than the ball rotating around the center of the cylinder?

Ahh, I got the right answer but I'm still a bit confused. I thought that the actual force working on a rolling ball was static friction...

So the only static friction force is the vertical component which is equal in magnitude to the weight?

But how can I compute the tangetial static friction force? I can find the normal force and therefore the max static friction, but this isn't necessarily the force that's acutally working on it. I really don't know how to compute this...

So how would I calculate the tangential static friction force in this situation? Wouldn't I need to know whatever other tangential force is causing the ball not to accelerate tangentially?

[SOLVED] Vertical circular motion help! Homework Statement A 17.4 g steel marble is spun so that it rolls at 171.0 rpm around the inside of a vertically oriented steel tube. The tube, shown below, is 13.0 cm in diameter. Assume that the rolling resistance is small enough for the marble to...

Also, the static friction pointing up is equal to the weight; it's proportionality to the normal force is irrelevant, since I'm assuming the ball doesn't spiral down.

True enough, but if in a problem they tell you the angular velocity is constant, there has to be a pretty sizable force counteracting the tangential static friction force. I'm assuming this is kinetic friction, but is this a safe assumption?

well obviously I've never seen something roll forever, but I've never seen something roll in a vacuum. I know air resistance will slow down any moving object, but I also agree that it would be near impossible to perfectly spin an object so it rolls without kinetic friction. My problem I guess is...

So kinetic friction can slow down a rolling object? This seems kind of counter-intuitive.

[SOLVED] Circular motion, static friction Homework Statement Hey, this is more of a concept question than a homework question, but here goes: If a ball is spun fast enough to move around the inside of a vertical cylinder at a roughly constant velocity for a few seconds without spiraling down...

Because acceleration due to gravity is independent of mass.

If you do use the water method, don't forget to include the atm pressure in the room and, if the object is submerged, the water pressure pushing down on the object from the top (which is found using the same method as finding the buoyant force).