When two identical objects traveling at the same speed collide head-on, an observer standing in the earth reference frame sees both objects changing direction?

No, I think. I'm not sure what the Q meant.

Answer: buoyancy forceexplanation: in simple terms, the principle states that the buoyancy force on an object is equal to the weight of the fluid displaced by the object, or the density of the fluid multiplied by the submerged volume times the gravitational acceleration, g. this is also known as upthrust.