The total mass of the train and its passengers is 750000kg. The train is traveling at a speed of 84m/s. The driver applies the brakes and the train takes 80s to slow down to a speed of 42m/s.

|F| = 393750  N

Explanation:

Given that,

Total mass of the train, m = 750000 kg

Initial speed, u = 84 m/s

Final speed, v = 42 m/s

Time, t = 80 s

We need to find the net force acting on the train. The formula for force is given by :

F = ma

So, the magnitude of net force is 393750  N.

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i guess it’s a and b