Recent content by EventHorizon4

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    Understanding Momentum Conservation in Particle Collisions

    Homework Statement A particle of mass m is moving along the x-axis with speed v when it collides with a particle of mass 2m initially at rest. After the collision, the first particle has come to rest, and the second particle has split into two equal-mass pieces that move at equal angles q > 0...
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    Moment of Inertia of a grouping of pennies

    Wasn't familiar until now with the "parallel axis theorem," but that seems to have been the ticket here. Using that to calculate the moment of inertia for the pennies NOT rotating on their center of mass, then adding all seven together, gets the answer. Thanks.
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    Moment of Inertia of a grouping of pennies

    I obviously know how to calculate the moment of inertia of a disc, but I just don't understand how to account for multiple discs all centered at different places in a plane. It doesn't seem like it can be one integration...that would be really ugly. So is there some sort of way to "add" the...
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    Moment of Inertia of a grouping of pennies

    Hi, An old GRE problem asks what the moment of inertia of seven pennies, arranged in a hexagon with one in the center, all touching each others' edges is, about the axis that passes through the center of the central penny and is normal to the plane of the pennies. Each penny is a uniform...
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    Energy required to ionize helium

    Well isn't the total energy of 79.0 eV minus that energy of 54.4 eV the answer? That's obviously the way it's supposed to be done. But I'm not seeing how you get to 54.4 in the first place. Can someone re-explain that please?
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    Schools How many grad schools to apply to?

    I'm sure this is a question that comes up a lot but I can't find an old thread on it, and I've seen a lot of varying advice all over. How many grad schools should I apply to? Personally, I'm an junior (will be a senior in the fall) physics major with a 3.9 overall and about a 3.8 in math...
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