Constant velocity of the mass center

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SUMMARY

The discussion centers on the concept of the mass center's velocity in two problems involving external forces. In problem 14.1, the mass center's velocity remains constant due to the absence of external forces, while in problem 14.16, gravity is considered an external force affecting the object's velocity. The key conclusion is that gravity influences the mass center's motion when present, differentiating the two scenarios. The clarification provided indicates that the first problem assumes an environment without gravity, such as outer space, while the second problem is set on Earth.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Familiarity with the concept of mass center
  • Knowledge of external forces in physics
  • Basic principles of gravitational acceleration
NEXT STEPS
  • Study the implications of external forces on motion in classical mechanics
  • Explore the concept of mass center in different gravitational environments
  • Learn about the effects of explosions on mass center dynamics
  • Investigate the role of gravity in various physics problems
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Students of physics, educators teaching mechanics, and anyone interested in understanding the dynamics of mass center motion under varying gravitational conditions.

cipotilla
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I have attached two very simple problems with their solutions. In the first problem the velocity of the mass center is not constant while in the second it is.

From my understanding, the mass center of a object that explodes continues to move as if the object had not exploded and if there are zero forces acting on it the velocity of the mass center is constant.

In problem 14.1 (the second page) the object has zero external forces, so I understand why the velocity is constant but in problem 14.16 (second page) we use the gravity acceleration to calculate the velocity of the oject even though there are zero external forces. Why do you consider the gravity in one problem and not in the other one?

Thanks.
 

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cipotilla said:
In problem 14.1 (the second page) the object has zero external forces, so I understand why the velocity is constant but in problem 14.16 (second page) we use the gravity acceleration to calculate the velocity of the oject even though there are zero external forces.
Gravity is an external force.

Why do you consider the gravity in one problem and not in the other one?
One explosion presumably occurs in outer space where there is no gravity, while the other occurs on the earth.
 
That makes sense! Thanks!
 

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