(show your work) What is the net force on the box shown below?
30 N
60 N
20 N
30
60 20
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Which changes of state do the labels represent? a: b: c:

Consider a system to be two train cars traveling toward each other. what is the total momentum of the system before the train cars collide?   kg • what must the total momentum of the system be after the train cars collide?   kg •  

In an experiment, how can i change human errors? be specific.