- #1

AspiringPhysicist12

- 16

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External images from the links have been added to this thread start

- Homework Statement
- A sand-spraying locomotive sprays sand horizontally into a freight car as shown in the sketch. The locomotive and freight car are not attached. The engineer in the locomotive maintains his speed so that the distance to the freight car is constant. The sand is transferred at a rate dm/dt = 10 kg/s with a velocity 5 m/s relative to the locomotive. The freight car starts from rest with an initial mass of 2000 kg. Find its speed after 100 s.

- Relevant Equations
- F_external = 0

If I consider only the freight car's mass and the mass dm that's added to the freight car as part of the system, then I get this answer:

https://ibb.co/QfKSqQ5

But if I consider the freight car's mass, the mass dm, and the locomotive car as part of the system (maintaining the locomotive has velocity u relative to the freight car), then I get this answer:

https://ibb.co/RNZCbgY

I want to understand why I'm getting 2 different answers in this problem.

https://ibb.co/QfKSqQ5

But if I consider the freight car's mass, the mass dm, and the locomotive car as part of the system (maintaining the locomotive has velocity u relative to the freight car), then I get this answer:

https://ibb.co/RNZCbgY

I want to understand why I'm getting 2 different answers in this problem.

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