1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Cue ball kinetic energy

  1. May 4, 2010 #1
    Hello , i need some help solving a few questions. please help :) thankyou

    a)A pool Cue exerted an average force of 160N on a cue ball over a distance of 0.012m How much work did the cue do on the ball.

    b)If all the work done on (a) was transformed into kinetic energy of 0.0200kg cue ball, what was the speed of the ball?

    c) Light from the sun reaches the earth in 8.3min. The speed of light is 3.00x10g m/s. in kilometer, how far is the earth from the sun?

    d)An electron travels at a unifor velocity of 3.2x10g m/s, how much time is required for a displacement of 1.0m?

    e)A person walks 5.0 km torwards the east in 2.0 hours,then 1.5 km towards the west in 0.5 hour, and finally 10.0 km torwards the east again in 2.25 hour. What is the person's average velocity?
  2. jcsd
  3. May 4, 2010 #2


    User Avatar
    Homework Helper

    Re: Physics

    You need to show some attempt before anyone here can help you.

    What is the definition of work done and kinetic energy?

    How would you find distance given speed and time?

    How do find time given distance and velocity?

    What are the individual velocities for the journey?
  4. May 5, 2010 #3
    Re: Physics

    well for a and b , i tried it. but i dont think it is correct.

    a) w=f^d

    b) Ek=1/2mv2
    i canceled , then ended up with √ 2x0.0200/1.92
    V= 0.14433756729741

    and for the rest of the questions i need help with the equations to use for.
    c,d,and e
  5. May 5, 2010 #4


    User Avatar
    Homework Helper

    Re: Physics

    You should have gotten

    [tex]v = \sqrt{\frac{2E_k}{m}}[/tex]

    Check it again.

    For c an d, if you multiply speed and time, what do you get?
  6. May 5, 2010 #5
    Re: Physics

    for c,d and e.
    C) i got 2490 km

    D)320 000 3.2x100 000


    i dont know what to do next?
  7. May 5, 2010 #6
    Re: Physics

    for b,
    i calculated again , is this one right?
  8. May 5, 2010 #7


    User Avatar
    Homework Helper

    Re: Physics

    What are you using for the speed of light and the speed of the electron? I don't think you mean 'g' to be 9.81 m/s2

    Ek is the work done in part a).
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook