We're at cruise on a beautiful day. Copilot reaches up and flips on the windshield wiper for his side. It immediately floats up off the glass and then departs the aircraft. I asked him what the heck he was doing and he responded that he wanted to see if it worked this high. I told him to assume that the other one would function in the same fashion at our current speed and that he should get busy on the dropped object report.