A bus is moving and lots of ppl jumping

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When passengers jump inside a moving bus, the classification of the force as internal or external depends on the defined system. If the system includes both the bus and the passengers, the force is internal. Conversely, if the focus is solely on the bus, the force is considered external. The distinction emphasizes the importance of how the system is defined in physics. Understanding this concept is crucial for analyzing forces accurately.
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A bus moving with constant velocity. Passengers inside all jump at once, is that external force or internal force?

THx.
 
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It depends - if you want to look at the force exerted on the entire system (people and bus) then it is an internal force. If you're only looking at the bus then it is an external force. It is important not to think that if the passengers are physiclly inside the bus then it must be an internal force no matter what.
For example, it might help to imagine the bus as simply a platform with people standing on it.
A force is internal if whatever that's exerting the force is part of the system. You can define what the system is however you want, depending what your trying to figure out.
 
I see. Thanks ~
 

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