What is the slowest Velocity possible?

  • Thread starter Chaos' lil bro Order
  • Start date
  • Tags
    Velocity
In summary, the minimum possible velocity is zero in classical terms and limited by the Heisenberg Uncertainty Principle in quantum-mechanical terms. In order for a car to have noticeable movement, we would have to wait for an incredibly long time due to the uncertainty in its velocity. There is no lower limit to velocity in both classical and quantum mechanics, and the question is impossible to answer due to the lack of a universal reference frame.
  • #1
Chaos' lil bro Order
683
2
This question may sound dumb, but what is the slowest Velocity possible?

Say a car is parked in a parking lot perfectly flat on the concrete ground, is the car perfectly still? Or does the interactions of the cars tire with the concrete produce a tiny flux in movement? I'm guessing that if there is a tiny flux in movement that it cancels out to zero for all macroscopic observations. Let's assume that all background noise is zero for the sake of argument.
 
Physics news on Phys.org
  • #2
In classical terms, the minimum possible velocity is quite obviously zero.

In quantum-mechanical terms, the minimum possible momentum is limited by the Heisenberg Uncertainty Principle. If you have no knowledge of where a particle is, you can have compete knowledge of its momentum. In such a situation, it can still be arranged for the particles involved to have zero velocity with respect to some observer.

It doesn't make much sense (i.e. it's not very useful) to describe a car with quantum mechanics; decoherence makes objects like cars behave purely classically.

- Warren
 
  • #3
Ok thanks, guess it was a dumb question.
 
  • #4
chroot said:
It doesn't make much sense (i.e. it's not very useful) to describe a car with quantum mechanics; decoherence makes objects like cars behave purely classically.

Well, for fun, you could do an estimation: take a car of 1000 kg, and assume that we know the position up to 10 micrometers.
That gives us an uncertainty on momentum of ~ 10^(-34) Js/ 10^(-5)m = 10^(-29) kg m/s, or an uncertainty in velocity of 10^(-32) m/s (given the mass of 1000 kg).

So, given that we know the position of the car up to 10 micrometers, and that the velocity is uncertain (and hence of the order of) 10^(-32) m/s, in order for us to notice a movement of the car (meaning, that it moves for more than 10 micrometers), we'd have to wait for: 10^(-5)/10^(-32) s = 10^27 seconds, or ~10^19 years, which is about one billion times the age of the universe. In the mean time, probably the car will have evaporated.
 
  • #5
I used to wonder if I might diffract if I walk through a doorway slowly enough. :biggrin:
 
  • #6
You'll diffracture if you're blocking Tsu's path. :tongue:
 
  • #7
Could the ratio of Planck length to Hubble time be a significant lower limit for quantized velocity?
 
  • #8
There's nothing special about the Hubble time. In fact, it's always changing.

As I've said, in both classical and quantum mechanics, there is no lower limit to velocity.

- Warren
 
  • #9
Since there is no "universal" referance frame regarding absolute static locality, the question is impossible to answer.
However, it CAN be reasonably inferred that there is no evidence in non-motion.
 

What is the slowest velocity possible?

The slowest velocity possible is known as zero velocity, or standing still. This occurs when an object has no movement or change in position over a certain period of time.

How is zero velocity different from negative velocity?

Zero velocity means there is no movement, while negative velocity means the object is moving in the opposite direction of the chosen reference point. In other words, negative velocity has a direction, while zero velocity does not.

Can an object have zero velocity while still moving?

No, an object cannot have zero velocity while still moving. Zero velocity means the object has no movement or change in position, so if the object is still moving, it has a non-zero velocity.

What is the relationship between velocity and acceleration?

Velocity and acceleration are related because acceleration is the rate of change of velocity. This means that a change in velocity, whether it is an increase or decrease, will result in acceleration. Conversely, a constant velocity means there is no acceleration.

Can an object have a velocity of zero but still have acceleration?

Yes, an object can have a velocity of zero and still have acceleration. This is because acceleration is not just a change in velocity, but also a change in direction. So even if an object has zero velocity, it can still have acceleration if it changes direction.

Similar threads

  • Mechanics
Replies
5
Views
5K
Replies
10
Views
3K
Replies
9
Views
1K
  • High Energy, Nuclear, Particle Physics
Replies
3
Views
2K
Replies
2
Views
1K
Replies
5
Views
1K
  • Beyond the Standard Models
Replies
2
Views
2K
  • Advanced Physics Homework Help
Replies
1
Views
2K
Replies
3
Views
1K
Back
Top