WAEC Physics 2017 Objective — Question 5
Question 5 of 50 from the West African Examinations Council (WAEC) Physics 2017 Objective paper, with the correct answer and a full explanation.
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Which of the following statements about a moving particle is correct?
- A. A. If the resultant force acting on the particle is zero, then it is in dynamic equilibriumCorrect
- B. B. If the resultant force acting on the particle is greater than zero, it is moving with a uniform velocity
- C. C. The rate of change of its momentum with time takes place in a direction opposite to that of its motion
- D. D. The particle falling freely covers equal distances in equal time intervals
Explanation
Given a horizontal surface, if the body has mass m kg, the frictional force (Fr) can be gotten from Fr=μ x R (friction=coeff. of static x normal reaction, where R=mg, opposite the weight of the body). Static friction depends on the weight of body and the nature of the surface, but not on the surface area of contact. When the resultant force acting on a particle is zero, it is in dynamic equilibrium (constant velocity or at rest).
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