Physics H131: Hints for Problem Set #16

Chapter N10 Problems

• N10S.9: (a,b) Write down the relevant equations for ballistic motion. What are the unknowns, and how many equations do you have to determine them? Do your results have reasonable orders of magnitude? (c) Which kind of ratio decides whether or not drag is negligible? Compute that ratio.
• N10S.11: From which component of the equation of motion do we get the range? Can this equation be solved right away? If not, from where can we get the missing information? How can you determine where a given function has its maximum?
• N10R.1: What is given, what are the unknowns? Which components of the equations for simple projectile motion apply here? Which equation gives us the initial speed? What does the other equation do for you? How does your result for the initial speed compare with the speed of sound? Can air friction really be neglected as claimed? Can Abel "stand" the jump?
• N10A.1: If you use the result from problem N10S.11 and the hint given in the problem, the solution is actually quite straightforward. [cos(phi) is an even function!]

Chapter N11 Problems

• N11B.3: Which of the given information is relevant, which isn't? How are spring constant and frequency related?
• N11S.3: Try to argue using energy conservation.
• N11S.5: Which are the extreme points between which the object will oscillate after being released? What does this imply for the equilibrium point? Which forces define the equilibrium at this point? At which point(s) of the oscillation does the object have the largest speed? Remember how to calculate the velocity when the position as a function of time is given.
• N11R.2:Consider the cord as a "1-sided spring", i.e. a spring whose potential energy increases only when stretched, but not when pushed together. To what extent, then, can you describe Larry's motion after he jumps as a harmonic oscillation? Do you really have to use a harmonic oscillator approach? Do you really need to know the oscillation frequency? What does simple energy conservation tell you?