A truck driver has a truckload of chickens (in a nearly sealed truck) which exceeds the maximum weight allowance. The driver's idea to trick the scale at a weigh station is to scare the chickens to make them fly inside the truck. Will this plan work?

A) Yes, the measured weight will decrease significantly.

B) Yes, the measured weight will decrease slightly.

C) No, there will not be a measurable difference.

Solution: C. Consider the system of the chickens, truck, and inside air as a system. The external forces before and after the disturbance are the upward force of the scale and the weight force. The weight force is the same (total mass is the same), and there is no acceleration, so the normal force (scale reading) remains the same.

Another way to look at this is from the point of view of the truck alone. When the chickens are standing, they exert a downward normal force on the truck (thus increasing its measured weight). When the chickens are flying, they are pushing air downward which must continuously smash into the truck bed (thus increasing its measured weight).