Tossing in Tangentials

E and F Blocks added tangential velocity and acceleration to our descriptors of circular motion. Both are instantaneous values with a straight line direction found through drawing the tangent line for the relevant point on the circle. Unlike angular velocity and acceleration, these values are not the same for every point on the object - they vary based on distance from the axis of rotation. The further away from the rotational axis, the larger they are and they decrease in size as we approach the center of the circle. Centripetal acceleration describes the rate of change of direction for the tangential velocity vectors and always points to the center of the circle. Make sure you can use both formulas to calculate centripetal acceleration, based on the velocity value you're given and we'll add in the force that promotes this acceleration tomorrow.

B Block discussed centripetal force in class and related it to our work yesterday on centripetal acceleration. Remember that "centripetal force" is a job description - many forces can serve this purpose and you might have to calculate the value of the centripetal force using Newton's ^nd Law of Motion or assess a normal force before moving on in a problem. We also began our discussion of gravity, which was cut short by the fire drill. Gravity is a force of attraction between all matter and can be calculated using Newton's Law of Universal Gravitation. We'll review this tomorrow very briefly before you start on your lab investigation.

C Block worked on their centripetal force lab, looking at the relationship between centripetal force, radius of rotation and speed of rotation. For your write-up, you only have to include the graphs, data tables and a concluding statement about the relationship between force and velocity versus force and velocity². We'll go over these tomorrow and use the lab to highlight some ideas about centripetal acceleration.