DAY 25 LETS GO! TODAY AT A GLANCE: 1) You try a math example and learn about pulleys. 2) We look at pulleys in a different way. 3) LOTS of learning/graphing and questions for pulleys

A) 153 upE) 45 up B) 153downF) 45 down C) 177 up D) 177 down

LETS GET OUT THE HW Questions?

T HEN … HQ QUIZ

TENSION AS A FORCE Tension is the force from a rope or string. A rope can only have 1 tension on it.

Put equal masses on each side. Now draw a FBD for each mass under your general picture..

Put unequal masses on each side. Now draw a FBD for each mass under your general picture. Remember to figure out which way the imbalance is!.

As one side gets more and more massive, what will happen to the acceleration? Is there a limit to the value? MY THINKING: “The weights oppose each other. As one gets heavier, its like the other weight is not really there. So its going be like its not opposed. Which would be free fall.

L ETS D O A N E XAMPLE T O S TART U S O FF Here is a massless pulley that rotates without friction. What does that mean? MAIN GOAL: What is the acceleration of these masses? SIDE GOAL: How much tension is there? 3 kg 7 kg

1 st : Draw a FBD on each Circle forces, label imbalance/balanced Next: Lets CREATE net force equations for this situation.

Lets solve for our: Main Goal: Side Goal:

Now for a new, fresh look: Draw this in your notebook front and center. CALL IT: Pulley on table Observe the setup

IN CLASS NOTEBOOK The graph: The reasoning:

IN CLASS NOTEBOOK

GOALS: 1) Determine how the acceleration relates to the weight hanging off the edge 2) Determine how the acceleration relates to the changing the mass on the top (table) but NOT changing the weight hanging off the edge.

GOALS: 1) Determine how the acceleration relates to the weight hanging off the edge More hanging weight = more acceleration in a directly proportional amount 2) Determine how the acceleration relates to the changing the mass on the top (table) but NOT changing the weight hanging off the edge. More mass on top = less acceleration because more mass is being moved by the hanging thing.

LETS SHOW IT Assume no friction, and the pulley and rope are mass less (WHY?)

DRAW A FBD FOR EACH Hanging MassTable Mass SYSTEM:

DO MORE So for the SYSTEM: And the tension:

QUESTION: Try the 1 st HW question for me. On the boards!

1) Any volunteers to tell me what they think? Possible Answers: Block B’s weight pulls it down. The imbalance is down, so the down pull MUST be larger than the up pull on B. The up pull is the tension, so it must be less. The amount of imbalance is the weight of B. That weight moves it and A. Since the tension is just moving A and NOT B, the tension is less than B’s weight.