Abody is moving in a perfect circle at a constant speed. are there any forces acting on this body? how do you know?

Yes, there are forces acting on a body moving in a perfect circle at a constant speed.

Although the speed of the object is constant but the direction is changing continuously. A force is needed to change the direction and that force is called as the centripetal force. So an object moving in a circular path at constant speed is acted by centripetal force.

the moon affects the earth gravitation ally, causing certain motions of that body and also producing tides in its ocean and atmosphere. the tidal wave in our atmosphere is, however, far too minute to be an effective cause in any known meteorological phenomenon.

explanation:

the part of the wave he is travelling on is the crest