A6000 kg train car traveling at 2.5 m/s collides with another 6000 kg train car, now they are both moving but with a speed of 1.25 m/s. this is an example of

A 6000 kg train car traveling at 2.5 m/s collides with another 6000 kg train car, now they are both moving but with a speed of 1.25 m/s. This is an example of Conservation of Momentum.You can prove it by (6000kg)(2.5m/s)+(6000kg)(0m/s= (6000+6000kg)(1.25m/s).

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Ohm's law tells you that i = v/r where v is equivalent voltage and r is equivalent resistance of the circuit
since all circuits have the same voltage, your question is really asking which circuit has the lowest total resistance, since the lower the resistance, the higher the current
circuit a has a resistance of 5 ohms; circuit c is in series so has a resistance of 10 ohms; circuit b is in parallel and therefore has a resistance of 2.5 ohms (review your notes on adding resistances in parallel and series); therefore b has the highest current