Suppose I have an 8kg bicycle with wheels weighing 2kg and I have an 8kg bicycle, but the wheels weigh only 1.5kg (we assume that the mass is gained at the height of the rims). Will I notice a difference between those 2 bikes when accelerating?
Answer
Getting a rotating mass in motion is very similar to getting a linearly moving mass in motion.
You have two eggs of the same size. One egg is hard-boiled, the other is uncooked. You let them roll down a slope at the same time. Which egg goes down first and why?
The uncooked egg.
The boiled egg.
They arrive at the same time.
A is the correct answer
In a boiled egg, all the parts of the egg are solid and connected to each other. This means that all the particles have to start spinning when the egg starts to roll. Energy is needed for that rotation. With an uncooked egg, only the viscous protein directly under the shell will rotate. The rest of the liquid does not rotate, but slides downwards, as it were. With uncooked eggs, less energy will therefore be converted into rotational energy, leaving more energy for the forward movement. This will cause the uncooked egg to roll down faster.
Answered by
dr. ir. Nico Smets
Engineering Sciences
Avenue de la Plein 2 1050 Ixelles
http://www.vub.ac.be/
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