NYA Lab Instructions - collision of pucks (F2008)

# NYA Lab Instructions - collision of pucks (F2008) - Physics...

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Physics NYA – Mechanics Dawson College Lab #4 – Collisions in Two Dimensions Introduction: Purpose The purpose of this experiment is to: Verify the conservation of linear momentum by observing the collision of two pucks on a flat air table. Verify that the centre of mass of such a system has a velocity that is unchanged by the collision. In addition, you will: Prepare an abbreviated report that contains only data, analysis and conclusions. It is not necessary for this report to include an Introduction or Procedure section. One third of the marks for your report will be based on your conclusion. Theory A - Conservation of Momentum An alternate way of expressing Newton’s 2 nd Law is with the linear momentum ( v p ). Linear momentum is defined in terms of the mass (m) and velocity ( v v ) as: v v p mv = (1) Newton’s 2 nd Law can be written in terms of linear momentum as: dt p d F ext v v = where ext F v is the sum of external forces acting on the mass. If the sum of all external forces is zero , then the time rate of change of linear momentum is also zero – that is, linear momentum doesn’t change . If we therefore define two particles about to collide as a single system, and if there are no other horizontal forces acting on this system (like friction) then the total momentum before and after the collision will be the same: 0 = = Δ before after p p p v v r (2) If the pucks are labelled so that L=light, H=heavy, a=after and b=before, the x and y-directions momentum conservation equations can be written as: x-direction : ( )( ) 0 , , , , , , , , , , = + + = a H x b L x a H x a L x b x a x p p p p p p and y-direction : 0 , , , , , , , , , , = + + = a H y b L y a H y a L y b y a y p p p p p p B – Centre of mass and momentum It is possible to identify the centre of mass (CM) of a two particle system – the point at which the two masses would balance were they attached by a rigid massless rod. The distance (d CM ) of the centre of mass from the lighter of the two masses along a line connecting them is given in terms of the total distance between the masses (D) and their masses as: + = L H H CM M M M D d (3)

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## This note was uploaded on 10/03/2010 for the course PHYS. 203-NYA-05 taught by Professor Ms.simpson during the Fall '09 term at Dawson College.

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NYA Lab Instructions - collision of pucks (F2008) - Physics...

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