Simple Nature - Light and Matter

Page 118, problem 5:E total,i = E total,fU i + heat i = U f + heat f + K f12 mv2 = U i − U f + heat i − heat f= −∆U − ∆heat√ ( )−∆U − ∆heatv = 2m= 6.4 m/sSolutions for Chapter 3Page 218, problem 4: A conservation law is about addition: it says that when you add upa certain thing, the total always stays the same. Funkosity would violate the additive nature ofconservation laws, because a two-kilogram mass would have twice as much funkosity as a pairof one-kilogram masses moving at the same speed.Page 219, problem 12: Momentum is a vector. The total momentum of the moleculesis always zero, since the momenta in different directions cancal out on the average. Coolingchanges individual molecular momenta, but not the total.Page 220, problem 15:a = ∆v/∆t, and also a = F/m, so∆t = ∆va= m∆vF(1000 kg)(50 m/s − 20 m/s)=3000 N= 10 sPage 221, problem 23: (a) This is a measure of the box’s resistance to a change in its stateof motion, so it measures the box’s mass. The experiment would come out the same in lunargravity.(b) This is a measure of how much gravitational force it feels, so it’s a measure of weight. Inlunar gravity, the box would make a softer sound when it hit.(c) As in part a, this is a measure of its resistance to a change in its state of motion: its mass.Gravity isn’t involved at all.Page 223, problem 34: (a) The swimmer’s acceleration is caused by the water’s force on theswimmer, and the swimmer makes a backward force on the water, which accelerates the waterbackward. (b) The club’s normal force on the ball accelerates the ball, and the ball makes abackward normal force on the club, which decelerates the club. (c) The bowstring’s normal forceaccelerates the arrow, and the arrow also makes a backward normal force on the string. Thisforce on the string causes the string to accelerate less rapidly than it would if the bow’s forcewas the only one acting on it. (d) The tracks’ backward frictional force slows the locomotivedown. The locomotive’s forward frictional force causes the whole planet earth to accelerate bya tiny amount, which is too small to measure because the earth’s mass is so great.933