Question

is it possible that a force changes only in the direction of motion without any change in the speed of an object .illustrate your answer with the help of an exmple  

Answer 1

Yes , it is possible for any force to change the direction of motion without any change in speed. See in the circular motion when any body is whirled around a string about a point the centripetel force acting towards it centre changes the direction of motion at every point keeping the speed constant if and only if we neglect friction and changing the velocity is different at each point, as the direction of motion at each point is different, so the there is a variable velocity and thus the motion is an uniform accelerated motion.
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