Explain me that how it is possible that if a force is acting on a moving body perpendicular to the direction of motion,then no change in speed will take but direction may change?

Lets say the object is moving in the y direction. The force is being applied in the x direction. The object will experience no change in speed in the y direction, however it will change speed in the x direction and will change overall course and magnitude of speed. I would check the wording but the speed will make no change in the y direction because there is simply no force to accelerate or deccelerate the object in the y direction.