question_answer 50)

  The velocity of a body moving in a straight line is increased by applying a constant force F, for some distance in the direction of the motion.

Answer:

  Consider an object of mass m moving with a uniform velocity u. Let, it now be displaced through a distance s, when a constant force F acts on it in the direction of its displacement. From the third equation of motion,                                                                                                              ?.(i) We know that, work done by F is  (since, force and displacement are in same direction so  [From Eq. (i)]  If the object is starting from its stationary position i.e., u=0, from Eq. (II), we get It is clear that the work done is equal to the change in the kinetic energy of an object.