Got Homework?
Connect with other students for help. It's a free community.
Here's the question you clicked on:
 0 viewing
superduper
Group Title
Regarding problem 6.5: can someone please explain why tennis ball velocity is 3v after colliding with basketball.
 3 years ago
 3 years ago
superduper Group Title
Regarding problem 6.5: can someone please explain why tennis ball velocity is 3v after colliding with basketball.
 3 years ago
 3 years ago

This Question is Closed

Owlfred Group TitleBest ResponseYou've already chosen the best response.0
Hoot! You just asked your first question! Hang tight while I find people to answer it for you. You can thank people who give you good answers by clicking the 'Good Answer' button on the right!
 3 years ago

mathfan Group TitleBest ResponseYou've already chosen the best response.0
The basketball clearly bounce back (up) with a speed of v and then collides with the tennis ball. From the frame moving with the basketball the tennis ball appears to collide with the basketball at a speed of 2v. Lewin then says that in the original frame the tennis ball has speed 2v+v=3v! Why are we adding? All help appreciated.
 3 years ago

julie Group TitleBest ResponseYou've already chosen the best response.2
All collisions are considered perfectly elastic. In the approximation, the tennis ball and the basketball collide at about the same height so by conservation of energy P.E.=K.E. and they have about the same speed v, but in opposite directions. so the difference in their relative velocities is 2v, i.e. If you were on the basket ball, you would see the tennis ball approaching and rebounding with a speed of 2v. But the basket ball is moving upward at a speed of v, so by gallilean transformaoin of frames, the tennis ball is moving upward with a speed of 3v in the frame of reference of the ground. A key assumption here is that the mass of the basketball is much larger than the mass of the tennis ball, so that the speed of the basketball effectively remains unchanged after the collision. Then by using mgh=1/2v^2, you can see that the tennis ball bounces off the basketball to a height approximately 9 times than if it were to just bounce off the ground
 3 years ago
See more questions >>>
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.