# Circular motion- counter intuitive [closed]

Why is it counter intuitive that for a particle moving in a circle is always being acted upon a force which is directed towards the centre of the circle and not towards the direction of the motion of particle?

• Why do you think it's counter-intuitive? – PM 2Ring Aug 14 '20 at 12:15
• This seems counter intuitive at first because we naively think of the acceleration vector as being parallel to the velocity vector, and either speeding an object up or slowing it down. Circular motion is the antithesis of this - the acceleration and velocity vectors are perpendicular and the speed of the object is constant. You can also have "in between" cases e.g. elliptical orbits. – gandalf61 Aug 14 '20 at 13:01

## 1 Answer

Look at it the other way round: if there's no force directed to some center point, a body will not move in a circle.

If you don't apply a force to a body, it moves in a straight line. Imagine a stone on a flat, slippery surface. It won't move in a circle.

So, if you observe something moving in a circle, there must be some force dragging it to the center. Imagine letting a stone at spinn around you, helfd by a string. It will only follow its circular movement as long as you pull hard on the string (apply a force directed to the center).

If you apply a force in the direction of the movement, the body will accelerate. On earth, often friction on the ground interferes, so again imagine a rock on a slippery surface.