I was studying for the Physics Olympiad (as you do
) when I got a question wrong in the exam paper, and I cannot figure out why.
The question is as follows:
An expert juggler, carrying five juggling pins, has to cross a swing bridge which has a maximum safe load rating of 50 kg. The juggler weighs 47 kg and each of his five pins weighs 2 kg. He believes he can make it across safely in one trip by juggling the pins, so that he is never holding more than one pin. His skill enables him to juggle smoothly without any jerking. He is
A. incorrect – more information is needed.
B. correct – the total weight will never exceed 49 kg
C. correct – no jerking means no extra weight.
D. correct – the total weight can be made to exceed 49 kg by an arbitrarily small amount.
E. incorrect – the total weight is 47 kg + 5x2 kg = 57 kg.
I chose D, because I though that the juggler's weight, plus the weight of the single pin would equal 49kg, but would be slightly exceeded by the force of acceleration.
But the correct answer is E, according to the examination's solution papers. This completely baffled me. How can the pin's weight affect the juggler's weight and the bridge when they contact neither? 