Back in the Saddle

After a long weekend, we hop right back into circular motion for the final blast before we hit rotational dynamics. B and E Blocks went over their homework for gravitational/centripetal forces and reviewed for tomorrow's exam. No very complex problems, but a lot of little ones to make sure you can work with the skills in the chapter. Still only 25 test items, though, and the short answer should be guaranteed points if you haven't been sleeping in class.

C and F Blocks reviewed their work on centripetal force and took a look at Newton's Law of Universal Gravitation today. Gravity is generated by all mass and the larger the mass, the stronger the gravitational field. As with all fields, as you distance yourself from the mass, the field gets weaker. So, combine those ideas and we get the notion that the force that arises when two gravitational fields overlap is directly proportional to the masses and inversely proportional to the distance between them. Specifically:

F_g = G(m₁m₂)/r²

This is an example of an inverse-square law, and we'll see several of them this year. Tonight's homework will allow you to practice with this formula and remember the head's ups I gave you in class: don't forget "G," don't forget to square/square-root the distance and make sure you can work with your calculator efficiently to punch in all those darned numbers and exponents. Although none of the problems have you work with a distance between two objects and then add the individual radii for your overall calculation, don't lose sight of the fact that the distance is measured between each object's center of gravity which, for a sphere is dead smack in the middle. We'll go over these problems tomorrow and start the review process for Thursday's exam.