Conservation of Angular Momentum & Energy question

In summary, the conversation discusses the effect of switching a streetcar from a larger circular track to a smaller circular track on its speed. The teacher mentions that the normal force from the track does work on the train during the switch, and this is key to solving the problem. The question of whether the force does work on the train is raised and it is clarified that the direction of the force from the rails is important in determining the answer.
  • #1
15ongm
7
0
2chorad.jpg

Question: A streetcar is freely coasting (no friction) around a large circular track. It is then switched to a small circular track. When coasting on the smaller circle its speed is:

a) greater
b) less
c) unchanged

Relevant
Formulas:
w = v/r
KE = 1/2mv2

My teacher said the normal force from the track on the train doing work as the train switches from the larger to the smaller circle and something about how the conservation of momentum is not valid in this situation. And when I looked this question up online, they saw that energy is conserved. However, I'm still confused on how to solve this problem and what the answer is (I think it's unchanged?).
 
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  • #2
15ongm said:
My teacher said the normal force from the track on the train doing work as the train switches from the larger to the smaller circle
Does the force from the track do work on the train? That's key.
 
  • #3
Doc Al said:
Does the force from the track do work on the train? That's key.
I think so? I remember my teacher saying something how the normal force does work on the train but I'm confused as to how it does.
 
  • #4
15ongm said:
I think so? I remember my teacher saying something how the normal force does work on the train but I'm confused as to how it does.
You are right to question it. What direction will the force from the rails be in, in relation to the direction of the train's velocity?
 

Related to Conservation of Angular Momentum & Energy question

1. What is conservation of angular momentum and energy?

The conservation of angular momentum and energy is a fundamental law of physics that states that the total angular momentum and energy of a closed system remains constant over time, regardless of any internal changes or external influences. This means that the total amount of angular momentum and energy in a system cannot be created or destroyed, only transferred or transformed.

2. How is angular momentum and energy conserved?

Angular momentum and energy are conserved through various physical processes such as rotation, translation, and interaction between objects. In a closed system, any change in the angular momentum or energy of one object will result in an equal and opposite change in another object, keeping the total amount constant.

3. What is the role of angular momentum and energy in the conservation of orbits?

In the conservation of orbits, angular momentum and energy play a crucial role in maintaining the stability and predictability of an object's motion around a central point. This is seen in planetary orbits, where the total angular momentum and energy of a planet remain constant, resulting in a stable and consistent orbit around the sun.

4. Why is conservation of angular momentum and energy important in physics?

The conservation of angular momentum and energy is important in physics as it is a fundamental law that governs the behavior of physical systems. It allows scientists to make accurate predictions about the motion and interactions of objects in a closed system, and it is essential in understanding various phenomena such as planetary motion, rotational motion, and collisions between objects.

5. Can conservation of angular momentum and energy be violated?

No, the conservation of angular momentum and energy is a fundamental principle in physics and has been proven to hold true in countless experiments and observations. While there may be apparent violations in certain situations, further investigation will reveal that the conservation law still holds, and any changes in angular momentum or energy can be accounted for through transfer or transformation within the system.

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