Force, Torque, Pressure and Momentum

Folks are in very different places today, but everyone is moving along nicely...

Physics A and B reviewed their work with the impulse-momentum theorem before turning attention to conservation of momentum. Conservation of momentum comes about through Newton's 3^rd Law of Motion - the impulse that acts on one object has to match the impulse that this object imparts to the object that touched it. Therefore, the momentum changes of each object are equal but opposite. One object gains momentum and the other loses it, but the total remains the same. Momentum is simply transferred between objects in the system. We looked at examples of situations from the perspective of conservation of momentum to highlight strategies for problem solving and folks worked some practice in class. We'll go over the homework practice tomorrow and toss in a little extra if need be to nail this concept down.

Intro Physics continued their discussion of Pascal's Principle and hydraulic devices. We looked at how hydraulic devices serve to multiply our effort force (something we'll later call mechanical advantage) and how to calculate the size of that force multiplication. Time was given in class to work problems involving hydraulic devices and tomorrow, depending on how much time we have with the pep rally stealing our instructional time, we may or may not do an investigation on density. We'll need a good understanding of density to work through the upcoming topics of pressure with depth and buoyant forces.

Honors Physics reviewed their work with Kepler's laws of motion and yesterday's lab on centripetal force before taking on the concept of torque. Torque is the rotational analogue of force - it serves to change the speed of rotation (produces angular acceleration). Centripetal force handles direction and torque handles speed in the rotational world. We looked at some demonstrations of how force and torque differ and how the angle through which the force is applied affects a force's ability to rotate an object. Your homework items will give you practice with torque, lever arm and rotation and we'll revisit these ideas on Monday when we start to look at simple machines.