Superman must stop a 115-km/h train in 160 m to keep it from hitting a stalled car on the tracks. The train's mass is 3.6 * 105 kg. Determine the force that must be exerted on the train.

Question

Physics

Johnny Joseph

23 September, 21:41

Superman must stop a 115-km/h train in 160 m to keep it from hitting a stalled car on the tracks. The train's mass is 3.6 * 105 kg. Determine the force that must be exerted on the train.

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Answers (1)

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Picasso · Answer 1

1.148*10^6 N

Explanation:

The kinetic energy of the train is ...

KE = (1/2) mv^2 = (1/2) (3.6*10^5 kg) (115 km/h * (1000 m/km) / (3600 s/h)) ^2

≈ 1.83681*10^8 J

This is the work required to stop the train, so is ...

F·d = KE

F = KE/d = (1.83681*10^8 J) / (160 m) = 1.148*10^6 N

The force required to stop the train is 1.148*10^6 newtons.