Ok, not sure if this is the right section - hope so. A friend and I are having a debate on if there's a 100% transfer of momentum from one object to another. For example, if I tossed someone into a water current going 100mph that eventually the person would also, without fail, reach 100mph. I said that there is a constant loss in the transfer of energy between one object and another especially via just friction. Placing your hand flat on an object and pushing it would be different. Sliding your hand across something will ALWAYS have some losses that will keep the object from reaching the same speed as your hand. The materials in use will dictate what percentage of loss there will be. E.G. Sliding two pieces of concrete against each other will get closer in speed than a piece of paper and air. For example: If I tossed a piece of paper into the water, only a small fraction of the energy in the water will have to be transferred to the piece of paper in order to get it up to 100mph. However, a larger fraction of the energy would have to be transferred to get a block of lead up to the same 100mph. I wholly don't agree that there is a 100% transfer in the energy from one body to another, and thus you can not always get something up to the same speed. Thoughts?