1
EXPERIMENT
6a
Inelastic Onedimensional Collisions
Objectives
•
to measure the momentum and kinetic energy of two objects before and after a
completely inelastic onedimensional collision
•
to observe that the concept of
conservation of momentum
is independent of
conservation of energy
, that is, the total momentum remains constant in an inelastic
collisions while the kinetic energy changes
•
to calculate the percentage of KE which will be lost (converted to other forms of
energy, notably heat) in a completely inelastic collision between an initially stationary
mass and an initially moving mass; and to compare this calculation with the result of
the elastic collision
Procedure
In this and the next experiment we will analyze collisions between two carts of varying
masses in the case where one of the carts is initially at rest.
The carts move on an air track.
Therefore, in order to insure that no energy due to the gravitational potential is created, you
should first make sure that your track is level.
In this lab we study the totally inelastic collision, by arranging that when two carts collide
they will stick together and move with some final velocity common to both masses. Thus, we
have only to measure the velocity of Cart 1 before
the collision and the common velocity of
the carts after
the collision, since of course the velocity of Cart 2 is zero before the collision.
For this purpose, we use two photogates (see Figure 1).
Each of them allows us to measure
the time it takes for the cart or carts to go through it. The photogates record times by sensing
the fins attached to the tops of the carts while they are moving through the photogates' light
beams.
Therefore the velocities for these labs are calculated by dividing the length of the fin
(NOT the length of the cart) by the time measured by the photogate (speed = length/time).
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Figure 1
:
The Initial State of the Carts Before the Collision
In these instructions Gate 1 has the controllers on it and Gate 2 does not.
Cart 1 has the fin
on it and Cart 2 does not.
Cart 2 is initially stationary.
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 Summer '08
 J.T.
 Physics, Energy, Kinetic Energy, Momentum

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