N EWTON ' S 2 ND LAW STATES THAT …… His second law defines a force to be equal to the differential change in momentum per unit time as described by the calculus of mathematics which Newton also developed. The momentum is defined to be the mass of an object times its velocity. (F=MA)

A CCELERATION = VELOCITY Since acceleration is a change in velocity with a change in time, we can also write this equation in the third form shown on the slide. The important fact is that a force will cause a change in velocity; and likewise, a change in velocity will generate a force. The equation works both ways. The velocity, force, acceleration, and momentum have both a magnitude and a direction associated with them. Scientists and mathematicians call this a vector quantity

E XAMPLES : The motion of an aircraft resulting from aerodynamic forces and the aircraft weight and thrust can be computed by using the second law of motion.

N ASA EXAMPLE OF MOTION. In this demonstration, a simple model of a satellite orbiting Earth is created from a large stationary ball and a smaller ball at the end of a string. The ball and string become a pendulum that tries to swing toward the middle of the globe. However, the ball travels in an orbit around the globe when it is given a horizontal velocity in the correct direction. Although the small ball attempts to fall to the center of the larger ball, its falling path becomes circular because of its horizontal velocity Adapted from NASA's "A Teacher's Guide With Activities", produced by the Microgravity Science and Applications Division, Office of Space Science and Applications, and NASA's Education Division, Office of Human Resources and Education. rld.htm