Warm Up March 12, 2013 • Do you think there is any truth to the statement: “When Chuck Norris does push ups, he doesn’t push himself up, he pushes the earth down.” Explain. vs.
Agenda • Warm Up • Review HW 10.3 • 10.4 Notes • Newton’s 3rd Law Investigation Lab • Cool Down
10.4 Newton’s 3rd Law • Newton’s 3rd Law of Motion: if one object exerts a force on another object, then the second objects exerts a force equal in strength in the opposite direction on the first object. Or… • “For every action, there is an equal but opposite reaction”
Why don’t action/reaction forces cancel? • Remember that balanced forces do not cause a change in velocity. • But on the last slide, we saw a lot of velocity changes. What’s up?! • Action-reaction forces do not act on the same object; they act on different objects!
Momentum • Momentum is a characteristic of an object in motion. • Momentum = mass x velocity • So, objects with greater mass have more momentum than less massive objects moving at the same velocity. • And if two objects have the same mass, the one with the greater velocity has the greater momentum.
Law of Conservation of Momentum • Momentum, unlike force, is conserved. • Momentum can be transferred from one object to another, but cannot be increased or decreased without an outside force.
Cool Down • None. • p. 399 #1-5 all • 10.4 Vocabulary Booklet (2 words on p. 393) Homework