Recent content by physicsfox

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    Conservation of energy springs.

    Why do you think the PEspring and PEgrav change at different rates? Think about this question: If an object falls from rest, from a height of h, the object has PE defined by mgh, and KE defined by 1/2mv^2. These also appear to change at different rates... yet you would probably agree that as...
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    What is the relationship between speed and radius for a car to avoid skidding?

    Also, it is important to understand that the static friction, the source of the net centripetal force, is at its maximum value, and does not change.
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    Need help w/ Angular Momentum please

    Try assuming the mass of the object is 1kg... Since momentum is p=mv, you now have the initial velocity, 15m/s, and the velocity at the top, 7m/s... Think carefully about the direction of the velocity at the top of projectile's flight launched initially at some angle. A sketch might help...
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    What happens when F > 90N in Atwood problem?

    In response to "BerryBoy's" post, I have answered the original question, and have shown the detail in my original posting. As an extension to the original question, assuming that a 90N horizontal force is the force that will result in the atwood and the block having a relative acceleration of...
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    Why Is My Calculation of Speed on an Inclined Plane Incorrect?

    Another method that uses "work = change in KE"... if you draw your freebody diagram, 3 forces act on the block, Fgravity, Fnormal, and Ffriction. The definition of Work is W=Fdcos(theta). Quantify the work done by each force, careful when determining theta for each. Fgx4metersxcos(70)... etc...
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    What happens when F > 90N in Atwood problem?

    Here’s a question for you all… but first some background (see jpeg attachment for sketch) Assuming all surfaces are frictionless (5kg on horizontal surface, two 2kg blocks on 5kg block), and the pulley has no mass, with what horizontal force applied to the 5kg block will the two 2kg...
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    Calculating Mass in a Canoe Swap: A Physics Problem

    It may be easier not to use a spot on the boat as your reference point (since the boat moves). Pick an arbitrary Xo, and then measure everything from that location, both before and after movement.
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    Calculating Mass in a Canoe Swap: A Physics Problem

    This question is about the position of the center of mass between the man, the woman and the canoe. Pick an arbitrary x position to measure from, and then determine the center of mass. When they switch positions, the center of mass remains at the same location. The forces that create the...
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    How Can the Bottom Block Receive Maximum Force Without Moving the Top Block?

    Looks good. Another example, where all the surfaces are frictionless, would be a 4kg block tethered to the top of the 5kg block via a horizontal string. Assuming the max tension the string could withstand is 12N, the string would be able to accelerate the 4kg block to a max amount of 3m/s/s...
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    How Can the Bottom Block Receive Maximum Force Without Moving the Top Block?

    Just to clarify, is the 12N MAX force applied to the 4kg block?? If it is, think of what force will accelerate the 4kg block forward, while it is positioned on top of the 5kg block. This force has a max value (12N). Associated with this max force is a max acceleration for the 4kg block. If...
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    A very tought physics sum I am having trouble with.

    For part (a) energy conservation is a good plan. The total mechanical energy remains constant... so thinking to set the initial KE equal the final PE is conceptually correct. However, the KE of a rolling hoop is significantly different than the KE of a sliding block (or hoop). Review in your...
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