Ch7_MalleyJ

Ch7_MalleyJ toc

Momentum

 * momentum refers to the quantity of motion that an object has - defined as "mass in motion"
 * momentum = mass * velocity p = m*v
 * momentum is a vector quantity - meaning that it is fully described by both magnitude and direction
 * an object has a large momentum if either its mass or its velocity is large, and vice versa
 * objects at rest do not have momentum
 * CHECK YOUR UNDERSTANDING:
 * 1a) 540 kgm/s east
 * 1b) 20000 kgm/s north
 * 1c) 80 kgm/s south
 * 2a) 40000 units
 * 2b) 60000 units
 * 2c) 40000 units
 * 2d) 80000 units
 * 3a) v tight end = 6 m/s, v halfback = 9 m/s
 * 3b) halfback and tight end have same = 540 kgm/s

Momentum and Impulse Connection

 * an unbalanced force always accelerates an object - either speeding it up or slowing it down (if the force acts opposite the object's motion, it slows the object down)
 * newton's second law come in to play when dealing with momentum because force now influences velocity
 * Force*time = impulse
 * m*∆v = change in momentum
 * impulse = change in momentum
 * elastic collisions - collisions in which objects rebound with the same speed as they had prior to the collision (characterized by a large velocity change, a large momentum change, a large impulse, and a large force)

Real-World Applications

 * the effect of collision time upon the amount of force an object experiences and the effect of rebounding upon the velocity change and hence the amount of force an object experiences - two big factors in real-life
 * follow through? increase time, increase velocity
 * rebounding involves a change in the direction of an object; the before and after collision direction is different
 * crushing is actually safer in a car crash, not rebounding - shock shock