The motion of a particle of mass m is described by the relation, y=ut-\frac{1}{2}gt^{2}, where u is the initial velocity of the particle. The force acting on the particle is

  1. A. F=m(\frac{du}{dt})
  2. B. F=mg
  3. C. F=m(\frac{dy}{dt})
  4. D. F=-mg

Correct Answer: D. F=-mg

Explanation

Acceleration is the second derivative of displacement with respect to time. a = \frac{d^{2}y}{dt^{2}} = -g. Therefore, force F = ma = -mg.

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