pavelcherepan Posted June 14, 2018 Share Posted June 14, 2018 Hi everyone! Stupid question in the topic. Obviously, radius is perpendicular to a tangent at a point of intersection, but can it be said that radius is perpendicular to the circle itself? Does such statement even make sense? Link to comment Share on other sites More sharing options...
LaurieAG Posted June 14, 2018 Share Posted June 14, 2018 An axle is perpendicular to the plane of a circular wheel but it is not quite a radius. Link to comment Share on other sites More sharing options...
pavelcherepan Posted June 14, 2018 Author Share Posted June 14, 2018 5 minutes ago, LaurieAG said: An axle is perpendicular to the plane of a circular wheel but it is not quite a radius. Why is the axle not quite radius if it does connect the center of a circle to its perimeter? Link to comment Share on other sites More sharing options...
DrP Posted June 14, 2018 Share Posted June 14, 2018 2 hours ago, pavelcherepan said: Why is the axle not quite radius if it does connect the center of a circle to its perimeter? It doesn't connect to the perimeter. It is perpendicular to the plane of the circle through the centre. The axle would then be perpendicular to the plane of the circle itself.... I don't see the radius being so - it is in plane with the circle and not perpendicular to it. Link to comment Share on other sites More sharing options...
pavelcherepan Posted June 14, 2018 Author Share Posted June 14, 2018 25 minutes ago, DrP said: It doesn't connect to the perimeter. It is perpendicular to the plane of the circle through the centre. Sorry, I don't follow. Could you elaborate please? Link to comment Share on other sites More sharing options...
DrP Posted June 14, 2018 Share Posted June 14, 2018 The axle goes through the centre of the circle... if drawn in 2d on a piece of paper the axle line goes straight up through the centre of the circle out of the page - perpendicular to the plane of the circle and the page it is on. It never touches the perimeter. The radius is drawn from the centre of the circle to the perimeter... it is in plane with the circle and the paper it is drawn on. It is parallel to the page - not perpendicular to it. So - the radius is parallel to the plane of the circle - or in plane with it. The axle is perpendicular to the plane of the circle. Maybe you could say it was perpendicular to the circumference at the point it meets it? Link to comment Share on other sites More sharing options...
pavelcherepan Posted June 14, 2018 Author Share Posted June 14, 2018 4 minutes ago, DrP said: Maybe you could say it was perpendicular to the circumference at the point it meets it? Yeah, that was what I was going for. Is that the case? Link to comment Share on other sites More sharing options...
DrP Posted June 14, 2018 Share Posted June 14, 2018 1 minute ago, pavelcherepan said: Yeah, that was what I was going for. Is that the case? That's basically the same as it being perp to the tangent though, no? I don't think you can say it is perpendicular to the circle imo. Being perpendicular to just one tiny infinitesimally small point on the circumference doesn't make it perp to the whole thing. The axle IS perp to the whole thing though like LaurieAG suggested. Link to comment Share on other sites More sharing options...
mathematic Posted June 14, 2018 Share Posted June 14, 2018 In general, when talking about angle between intersecting lines (curves) the angle is between tangents at the point of intersection. Radius is perpendicular to tangent, therefore perpendicular to circumference at that point. Link to comment Share on other sites More sharing options...
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