Defying gravity
Edited BY: Helen Wolfson
Edit Date: 2017-05-22 14:20:59

First, watch the experiment below:

English version:

Hebrew version:

If you are already familiar with basics of circular motion, skip straight to the question. The theoretical background brought below contains clues for the answer.

In physics, circular motion is a movement of an object along the circumference of a circle or rotation along a circular path. Examples of circular motion include: an artificial satellite orbiting the Earth at constant height, a stone which is tied to a rope and is being swung in circles, a car turning through a curve in a race track, an electron moving perpendicular to a uniform magnetic field and many more.

Since the object's velocity vector is constantly changing direction, the moving object is undergoing acceleration by a centripetal force in the direction of the center of rotation. Without this acceleration, the object would move in a straight line, according to Newton's laws of motion. If we take, for example, a marble rotating inside a cone, the forces acting on the marble are shown below:

N- the normal force- is applied by the surface perpendicularly. The horizontal component of the Normal force is the centripetal force, which keeps the marble rotating around the glass circumference.

Mg- the gravitational force- applied by the earth towards the center of the earth. For more information about the value of g, watch the BLOSSOMS video:

 If both the marble  and the cone  are smooth, friction can be neglected.

Question: Would the marble rise to the same height as in the wine glass, when using the coffee cup shown in the video?

Question Created By: Helen Wolfson
Creation Date: 2017-05-13 09:14:14
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