# Circular Motion

Published on: Wed Feb 24 2010

We reviewed a another Force problem, force applied to an object from an angle. This force can be though of to have two components. We used Newton’s second Law, and broke it down into three equations. One for each axis (x and y) and one for The vector sum. We thought about how both x and y must sum to 0, for y there is only one force to be concerned about (Fexternal sin θ). But for the x direction we need to consider friction as well. Since it is pushing against our origin we think of Friction as a negative force. So Friction and the x force must sum to zero as well. We needed one more thing to solve the problem; the magnitude of the friction force. To find it we multiplied the Normal force by the Coefficient friction of kinetic force. (mu μ). We rearranged our equations, and then divided by each other to combine them into one. And now we know how to calculate the Normal Force and the external Force. Since we know those two we can calculate other things we may need too. Circular Motion We just started to touch on circular Motion. If you swing an object in a circle, the magnitude of velocity is constant, but the direction changes all the time. At one time it is in one spot, then a short time later it is a little further along. The magnitude of the radius at time 1 is equal to the radius at time 2. But the directional change is caused by a little vector called “Delta r” which pushes the direction of the vector along. The change in time is expressed by “Delta t” And the velocity is the change in r (Delta r) over the change in time (Delta t) Velocity is the tangent formed by Change in r over change in t. This makes Velocity almost a right triangle, when the distance in the change in time is very small.