F=ma, no acceleration with constant velocity?

In summary, the conversation discusses the concept of force and its relation to Newton's second law. The speaker is confused about how to calculate the force of a 30kg rock traveling at a constant speed in space. They are also unsure about the difference between force and momentum. The expert explains that forces only occur during interactions between objects and that the rock will only experience forces during the impact with another object.
  • #1
PhotonW/mass
15
0
I got a 30kg rock in space, no gravity, no friction. It is traveling at a CONSTANT speed of 100m/s. According Newton's second law, There should be NO force because there is NO acceleration. But I know if it hits another object it will either move the object or put a hole in it so I know there is force there but according to F=ma there is no force. How do I calculate the force?

Please, I am not taking physics, so I am learning this on my own. So please try to put this in words a layman can understand.
 
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  • #2
Sure, there is force during the impact, but when it isn't accelerating, no force.
 
  • #3
You may be having a common misunderstanding about forces. Forces describe interactions between objects, it is not a property of the objects themselves. If an object is not interacting with another object or field, then there are no forces at work.
 
  • #4
PhotonW/mass said:
... But I know if it hits another object it will either move the object or put a hole in it so ...

Sounds like your intuitive idea of 'force' is closer to 'momentum.'
 
  • #5
Your rock, moving freely in space was force free until the instant that it collided with the second object. When the collision occurred, there were forces imposed on your rock, and it was no longer a force free motion. It still obeys F = ma, but at that instant, F becomes nonzero, and therefore a becomes nonzero as well. As long as your rock is in contact with the second body (or any subsequent body), it will not be a force free motion. Whenever contact is broken, force free motion will again obtain, but it will be a new force free motion.
 

FAQ: F=ma, no acceleration with constant velocity?

1. What does F=ma mean?

F=ma is the equation for Newton's second law of motion, which states that the force (F) acting on an object is equal to its mass (m) multiplied by its acceleration (a). This means that the greater the mass of an object, the more force is needed to accelerate it, and the greater the acceleration, the more force is needed to achieve it.

2. How does F=ma apply to objects with no acceleration?

When an object is not accelerating, its velocity remains constant. This means that the acceleration (a) in the equation is equal to 0. Therefore, F=ma becomes F=m(0), which simplifies to F=0. In other words, when an object is moving with constant velocity, there is no net force acting on it.

3. Can an object have a non-zero velocity and still have no acceleration?

Yes, an object can have a non-zero velocity and still have no acceleration. This occurs when the object is moving at a constant speed in a straight line without changing its direction. In this case, the object's velocity is constant, and there is no change in its acceleration.

4. What is the difference between acceleration and velocity?

Acceleration and velocity are both physical quantities that describe the motion of an object. Velocity refers to the rate at which an object changes its position over time, while acceleration refers to the rate at which an object changes its velocity over time. In other words, acceleration is the change in velocity divided by the change in time.

5. How is F=ma used in real-world applications?

F=ma is a fundamental equation used in many fields of science and engineering, including mechanics, physics, and aerospace engineering. It is used to calculate the force needed to accelerate an object, which is essential in designing and understanding the motion of objects such as vehicles, airplanes, and satellites. It is also used in everyday applications, such as calculating the force needed to push or pull an object, or the force needed to stop a moving object.

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