Freight Car Velocity: Newton's 1st Law Explained

In summary, the conversation is about the effects of a leak in a railway freight car carrying sand on the car's velocity. It is determined that according to Newton's 1st law, the car's velocity would remain constant unless acted upon by an external force, which is not the case in this situation. However, there is confusion about the sand falling out and whether it affects the car's velocity. Using Newton's 2nd law, it is concluded that the mass of the sand leaving the car does not increase the car's velocity, as the sand itself has its own velocity and momentum.
  • #1
mini_mia
5
0
Hey guys!

I was wondering if I could get some help with this question:

A railway freight car that is carrying sand is traveling at a uniform velocity on a straight level track. A leak develops in the flat bottom, and the sand begins to pour out of a hole onto the ground. Assuming there aren't any external forces on the car (including friction), does the velocity of the car decrease, increase or remain the same?

According to Newton's 1st law, it says that the velocity of an object will remain constant unless it's acted upon by an external or unbalanced force, which there isn't any in this question. However, I am a bit confused about the sand falling out. Do this affect the velocity of the car? Thanks if you can help me!
 
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  • #2
What does Newton's second law say about this situation? Remember that Newton's second law can be written as a relation between the net force and the rate of change of momentum.
 
  • #3
Okay, so Newton's 2nd Law in terms of momentum is Δp = F Δt , which is also
F Δt = m Δv.

So in isolating velocity from the formula, as the mass decreases, the velocity would increase?
 
  • #4
That is incorrect. Yes the mass of the sand is leaving the car, but the sand itself has a velocity and therefore takes it momentum with it.
 

1. What is Newton's First Law?

Newton's First Law is also known as the Law of Inertia. It states that an object at rest will remain at rest unless acted upon by an external force, and an object in motion will remain in motion at a constant velocity unless acted upon by an external force.

2. How does Newton's First Law apply to freight car velocity?

In the context of freight car velocity, Newton's First Law explains that a freight car will continue to move at a constant speed unless acted upon by an external force, such as friction or a change in the force of the locomotive pulling it.

3. What factors affect the velocity of a freight car?

The velocity of a freight car can be affected by various factors such as the force of the locomotive pulling it, air resistance, the weight and size of the cargo, and the condition of the rail tracks.

4. How is the concept of inertia related to freight car velocity?

Inertia is the tendency of an object to resist changes in its state of motion. In the case of freight car velocity, the concept of inertia explains why a freight car will continue to move at a constant speed unless acted upon by an external force.

5. How can understanding Newton's First Law help improve freight car velocity?

By understanding Newton's First Law, engineers and scientists can design more efficient locomotives and rail systems that minimize external forces acting on freight cars and thus improve their velocity and overall performance.

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