Gotta Love that Newton

Today was filled with Newton's Laws of Motion, with some weight and normal force thrown in for color.

B and C Blocks reviewed their N-2 and N-3 homework, then moved into a discussion of weight and the normal force. Keep in mind when working problems that mass is not weight - you cannot stick an object's mass into a problem when weight is the necessary property. Also, watch out for problems where the situation does not take place on Earth or is in a location on Earth where they provide a specific value for gravitational acceleration. Then "g" will be whatever the value is for that location and not the familiar 9.81 m/s². A good calculation of weight is critical when assigning a value for normal force in a problem. A surface responds to the push applied on it by an object, so we need the size of that push to determine the response. For horizontal surfaces, F_N = F_g. Easy as pie. On an incline; however, because the normal line to the surface is not parallel to the direction of weight, only a portion of that weight generates a responding normal force: F_N = mgcosΘ. The other component of the weight - mgsinΘ - acts to accelerate the object down the ramp and factors in when assessing motion of the object up or down the ramp. Normal force, itself, plays a starring role in determining role in the frictional force an object experiences, so we will take time to make sure we can accurately calculate the normal force acting on an object before we start to tackle friction. The lab you guys will run for this unit will investigate friction in detail, so that should help clarify a lot of the concepts we'll discuss in class.

E and F Blocks had a discussion of Newton's Laws of Motion, with E Block making it through Newton's 3rd Law and F Block making it through Newton's 2nd Law. We'll pick up with weight and the normal force for E Block tomorrow and conquer Newton's 3rd Law of Motion and weight for F Block.