Activity Spend time observing or thinking about events that involve matter and energy. Which events can you
explain? Which events can't you explain? Now answer the following questions. Part A: describe three events that you cannot explain.
Part B: ask a testable question about each event you listed in part A. Part C: write a hypothesis for each testable question you listed in part B. Remember, a hypothesis can be proven right or wrong, so make your best guess. Part D: pretend you have a well equipped-lab with every testing device imaginable. What would you measure to test the hypotheses you listed in part C?

Three different objects, all with different masses, are initially at rest at the bottom of a set of steps. each step is of uniform height . the mass of each object is a multiple of the base mass : object 1 has mass 4..00m , object 2 has mass 1..96m , and object 3 has mass . when the objects are at the bottom of the steps, define the total gravitational potential energy of the three-object system to be zero. if the objects are then relocated as shown, what is the new total potential energy of the system? each answer requires the numerical coefficient to an algebraic expression. each algebraic expression is given using some combination of the variables , , and , where is the acceleration due to gravity. enter only the numerical coefficient. (example: if the answer is 1..23mgd , just enter 1.23)

Aperson stands on a platform, initially at rest, that can rotate freely without friction. the moment of inertia of the person plus the platform is ip. the person holds a spinning bicycle wheel with its axis horizontal. the wheel has moment of inertia iw and angular velocity ωw. take the ωw direction counterclockwise when viewed from above. part a what will be the angular velocity ωp of the platform if the person moves the axis of the wheel so that it points vertically upward?

You've already seen the value of 9.8 in this lesson. what's this value called? what quantity does it represent?