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FizziksGuy

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    AP Physics 1 Momentum Supplemental Problem 7b

    In AP Physics 1/2

    Posted

    Hi Maren,

         The positive/negative impulse implies direction.  By Newton's 3rd Law, if the block applies an impulse to the ball of 10 N*s, the ball must apply an impulse back to the block of 10 N*s in the opposite direction, therefore the block experiences an impulse of -10 N*s.  Since its mass is 0.5 kg, its change in velocity must be -20 m/s.  If it's going 20 m/s in the positive direction, and experiences a change of -20 m/s, that leaves it at 0.

         Think of it this way.  As the block travels to the right (positive direction) and hits the ball, it pushes the ball to the right, so the ball receives a positive impulse.  Likewise, the ball must push the block to the left, so the block receives a negative impulse.

         This is not a realistic problem, but from a theoretical standpoint it walks you through some of the key points of momentum.  The area under a force-time curve gives you the impulse (calculated in part A).  In part B, you use the impulse-momentum theorem to find the change in the ball's velocity.  In part C, you use Newton's 3rd Law coupled with the impulse momentum theorem to find the velocity of the block after the collision.  And in part D, you utilize the definition of a elastic vs. inelastic collisions.

    Problem related to power

    In Homework Help

    Posted

    Hi SamDiab.  What have you done so far to get started in this problem?  If it has you stumped so far, I'd recommend listing what is given, what you're asked to find, and then looking for potential relationships between the two.  For example:

     

    m=1.2 kg

    h=1.4 m

    t=8 hrs = 28,880 s

    P= 0.50 hp = 37.28 W

    Find: mass lifted (then you can divide by 1.2 kg/brick to get number of bricks)

     

    Video Discussion: Brainiac - Electric Fence

    In Video Discussions

    Posted

    Name: Brainiac - Electric Fence
    Category: Electricity & Magnetism
    Date Added: 2017-12-18
    Submitter: FizziksGuy

    Electric Fence Experiment Richard Hammond shows the Brainiacs how fun Electricity can be. Also, yes, if you are in the air when the electricity goes through, you don't get a shock. You don't get shocked if the circuit (box to fence to person to ground to box) doesn't complete. On top of that, the end where he ALMOST shakes Hammond's hand, he doesn't. Also, the slight gap in time between feet hitting ground and the shock can be attributed to the 1-2 second delay caused by the fence not being constantly on.



    Brainiac - Electric Fence

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