{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Ch9 HW2 - WebAssign Ch9 HW2(Homework Current Score 58 out...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Ch9 HW2 (Homework) Arthur Barfield PHYS 2211, section M, Fall 2008 Instructor: Jennifer Curtis Web Assign Current Score: 58 out of 59 Due: Friday, October 31, 2008 09:00 AM EDT Description Momentum and energy in collisions: Unequal masses; 2D collisions Instructions Reading: CH9 The due date for this assignment is past. Your work can be viewed below, but no changes can be made. 1. 9/9 points In outer space rock 1, with mass 6 kg and velocity < 3700 , -3200 , 1800 > m/s, struck rock 2, which was at rest. After the collision, rock 1's velocity is < 3200 , -2700 , 2100 > m/s. What is the final momentum of rock 2? 2 f = < 3000 3000 , -3000 -3000 , -1800 -1800 > kg · m/s Before the collision, what was the kinetic energy of rock 1? K 1 i = 8.151e7 8.15e+07 J Before the collision, what was the kinetic energy of rock 2? K 2 i = 0 0 J After the collision, what is the kinetic energy of rock 1? K 1 f = 6.582e7 6.58e+07 J Suppose the collision was elastic (that is, no change in kinetic energy and therefore no change in thermal or other internal energy of the rocks). In that case, after the collision, what is the kinetic energy of rock 2? K 2 f = 1.569e7 1.57e+07 J On the other hand, suppose that in the collision some of the kinetic energy is converted into thermal energy of the two rocks, where E thermal,1 + E thermal,2 = 1.10 10 7 J. What is the final kinetic energy of rock 2? K 2 f = 4.69e6 4.69e+06 J In this case (some of the kinetic energy being converted to thermal energy), what was the transfer of energy Q (microscopic work) from the surroundings into the two-rock system during
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
the collision? (Remember that Q represents energy transfer due to a temperature difference between a system and its surroundings.) Q = 0 0 J Solution or Explanation sys = net t = 0, so the momentum of the system doesn't change. Therefore, 1f + 2f = sys,i If the collision was elastic then K 1f + K 2f = K sys,i If some kinetic energy is converted into the thermal energy of the two rocks, then K 1f + K 2f + E thermal, sys = K sys,i Although the system's temperature rises (associated with the increase in its internal or thermal energy), in the rapid collision there isn't time for any significant thermal energy transfer Q to the cooler surroundings. Eventually the system will cool down as a result of thermal energy transfer to the surroundings, but this will take a while. 2. 22/22 points Object A has mass m A = 9 kg and initial momentum A,i = < 16 , -8 , 0 > kg · m/s, just before it strikes object B, which has mass m B = 11 kg. Just before the collision object B has initial momentum B,i = < 5 , 7 , 0 > kg · m/s. Consider a system consisting of both objects A and B. What is the total initial momentum of this system, just before the collision? sys, i = < 21 21 , -1 -1 , 0 > kg · m/s The forces that A and B exert on each other are very large but last for a very short time. If we choose a time interval from just before to just after the collision, what is the approximate value of the impulse applied to the two-object system due to forces exerted on the system by objects outside the system?
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern