Quantcast

A community for students. Sign up today!

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

DLS

  • 2 years ago

At the same instant that a 0.50-kg ball is dropped from 25 m above Earth, a second ball, with a mass of 0.25 kg, is thrown straight upward from Earth’s surface with an initial speed of 15 m/s. They move along nearby lines and pass without colliding. At the end of 2.0 s the velocity of the center of mass of the two-ball system is:

  • This Question is Closed
  1. mayankdevnani
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    options??

  2. DLS
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    A. 11 m/s, down B. 11 m/s, up C. 15 m/s, down D. 15 m/s, up E. 20 m/s, down

  3. DLS
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    V(a)=20m/s V(b)=-5m/s

  4. mayankdevnani
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Since this is multiple choice, lets use 10 m/s^2 as the acceleration due to gravity.

  5. DLS
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    so 0.50*20+0.25*(-5)/0.75

  6. mayankdevnani
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    The trick is to look at the momentum of the system after 2 seconds. So for the heavy ball, after two seconds, it has a velocity of -20 m/s.

  7. DLS
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    10+1.25/0.75 (wil we have a minus sign or are we considering just the mag?

  8. mayankdevnani
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Thus it has a momentum of -10 kg*m/s.

  9. DLS
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    u took downwards negative?

  10. mayankdevnani
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    yaa, i took downwards negative. The light ball will have a velocity of -5 m/s (15 m/s going up minus 20 m/s due to gravity gives 5 m/s downward). So it has a momentum of -1.25 kg*m/s.

  11. mayankdevnani
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    In both cases, the negative sign indicates the momentum is downward, and the sum is -11.25 kg*m/s.

  12. mayankdevnani
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Find the velocity of the system by dividing by the total mass (0.75 kg)?? then solve it and you get your answer.

  13. DLS
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    i took downwards positive and upwards negative,im getting something different

  14. mayankdevnani
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    no, always took downwards negative and upwards positive

  15. DLS
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    v=0+10*2 v=20m/s downwards and v=15-20 v=-5m/s upwards

  16. mayankdevnani
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    no!!!!

  17. mayankdevnani
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Find the velocity of the system by dividing by the total mass (0.75 kg) and you get 15 m/s down. so your answer is option C) 15 m/s up.

  18. DLS
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    wait u messed up!!

  19. mayankdevnani
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    no,, 15 m/s down.

  20. DLS
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    im taking downwards negative and upwards positive so for the 0.25 kg ball, v=15+20=35? we are taking upwards positive right

  21. mayankdevnani
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    right

  22. DLS
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    0.25*35=8.75

  23. DLS
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    -20+8.75

  24. DLS
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    oh :o

  25. DLS
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    -11.25/0.75=-15m/s

  26. DLS
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    i see! :D

  27. mayankdevnani
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    okk

  28. Not the answer you are looking for?
    Search for more explanations.

    • Attachments:

Ask your own question

Ask a Question
Find more explanations on OpenStudy

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
  • 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.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.