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Homework Help: Momentum dealing with 1D Collisions

  1. Oct 15, 2008 #1

    A block of mass m1 = 1.0 kg slides along a frictionless table with a velocity of +10 m/s. Directly in front of it, and moving with a velocity of +3.0 m/s, is a block of mass m2 = 9.0 kg. A massless spring with spring constant k = 1120 N/m is attached to the second block as in the figure below.

    (b) After the collision, the spring is compressed by a maximum amount Δx. What is the value of Δx?
    (c) The blocks will eventually separate again. What is the final velocity of each block measured in the reference frame of the table?
    m/s (for m1)
    m/s (for m2)

    I am having distinguishing the type of collision.
    Is this inelastic since the first block will "stick" compressing the spring?
    but it will soon separate so Im not sure if this is inelastic or elastic collsion.

    Momentum for M1 = m1 * v1 = 1kg * 10m/s
    Momentum for M2 = m2 * v2 = 3kg * 9m/s

    Can someone clarify if this is elastic or inelastic? and how would I approach this problem
  2. jcsd
  3. Oct 16, 2008 #2


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    Homework Helper

    Hi maniacp08,

    You have to be careful here with what "collision" means. The collision begins when the objects start putting forces on each other and ends when they stop. So we would not say the first block sticks to the second (as in a completely inelastic collision), because here that occurs in the middle of the collision.

    What exactly does it mean for a collision to be elastic? And what is happening to the energy during and after the collision?
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