A playful farmer is returning home from his farm carrying two huge 
pineapples, each one weighing 5 pounds.

Tired from working at the farm, he decides to take the short way 
home where he has to cross an old bamboo foot bridge. When he 
reaches the bridge, he sees a posted sign that reads "maximum 
bridge capacity - 200 pounds".

The farmer weighs 195 pounds. With the two pineapples his total 
weight is 205 pounds and exceeds the bridge capacity. Feeling 
tired, he does not want to make three trips across the bridge to 
bring one pineapple at a time.

A playful man, he thinks that if he juggled the two pineapples, 
leaving one up in the air and holding only one pineapple at any 
time, his total weight will be 200 pounds and he can cross the 
bridge safely.

He does exactly that. He juggles very good and does not drop the 
pineapple on the bridge. But soon the bamboo bridge breaks and 
he falls into the shallow river below.

Why did the bridge fall?

Assume that everything is correct - that the weights are accurate 
and the bridge will collapse if the force acted on it exceeded 200 
pounds.

 

Hint:

This is not a trick question but a scientific one.

Do not consider anything not mentioned in the story, such as a strong gusty 
wind that might have blown down the farmer, or heavy rain that might soaked 
him down and made him heavier. Consider only those things mentioned in 
the story and assume they are true and accurate.