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    Here is the Q...

    For a particle moving in a circle with uniform speed, which one of the following statements is correct?

    A) The kinetic energy of the particle is constant.

    B) The force on the particle is in the same direction as the direction of motion of the particle.

    C) The momentum of the particle is constant.

    D) The displacement of the particle is in the direction of the force.


    I was in the middle of picking either option A or B.

    I assume that the mass of the particle will always stay the same and that momentum is 'm*v', where v is uniform (constant throughout) so isn't momentum the same too

    Kinetic energy is '1/2 m v^2' and mass is again the same again with 'v' too so KE is constant.

    I found that the answer is A.

    Why is that???

    Can someone please explain! Would really appreciate it.

    Thanks.
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    It cannot be B because the force is centripetal since the particle is in circular motion.
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    The kinetic energy of a particle is a function of it's speed, not velocity (looking at it as a vector, you would use the modulus of its velocity). Particle's speed is constant, so its kinetic energy is constant.
    Edit: momentum is a function of velocity, so is not constant in circular motion.
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    Thanks a lot man. That does answer it for me. Thanks again.
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