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Homework Help: Energy Equations

  1. Mar 8, 2010 #1
    A 1.75 kg block slides with a speed of 0.880 m/s on a frictionless horizontal surface until it encounters a spring with a force constant of 787 N/m. The block comes to rest after compressing the spring 4.15 cm.

    Find the spring potential energy, U, the kinetic energy of the block, K, and the total mechanical energy of the system, E, for compressions of (a.) 0 cm, (b.) 1.00 cm, (c.) 2.00 cm, (d.) 3.00 cm, (e.) 4.00 cm.


    I've been using the equations:

    spring potential = 1/2*force constant*length^2
    kinetic = 1/2*m*v^2
    total = Spring + kinetic
  2. jcsd
  3. Mar 8, 2010 #2
    Start with Newton's Laws, write down the equations of motions and go from there
  4. Mar 8, 2010 #3
    With the three equations you have, you should get to the right answers. Maybe you want to actually show us what you did, and we will tell you if you did it right.
  5. Mar 8, 2010 #4
    I've been using those equations and plugged them in (we use an online website) and it was right the first time, and now its not...and logic would state that doing it again would yield correct answers...but I'm not getting them! Why? I haven't a clue.
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