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Cleonis
Cleonis
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I will start this answer with a general discussion, and then I will go to your question specifically.

There is the principle of relativity of inertial motion.

Example: let there be two trains, and they have a velocity relativity to each other. If you are a juggler, and you are performing inside a train carriage, can you tell from how the balls are moving on which train you are? You cannot; it feels the same. The only time you notice something is when the train undergoes a change of velocity.

A further implication of the principle of relativity of inertial motion is that while you can definitely tell when the train is changing velocity, whether you count that as an acceleration or a deceleration is arbitrary.

Whether you count a particular change of velocity as an acceleration or a deceleration follows from your choice of reference.

Of course, here on Earth the obvious choice is to use the entire Earth as reference of zero velocity. But the Earth has its daily rotation, and there is the motion of the Earth around the Sun, and there is the motion of our solar system around the center of mass of our Galaxy, etc.

My point is, distinction between acceleration and deceleration is not a measurable. What is measurable is how much change of velocity there is.



To your question specifically:

There is the amount of kinetic energy that must be transferred to an object in order to bring it up to a particular velocity $v$ relative to the reference coordinate system.

For a vehicle such as a car the obvious reference of velocity is the road. The speedometer of the car gives the velocity relative to the road.

There is the amount of kinetic energy that must be transferred to a car to bring it up to a particular velocity $v$.

Conversely, when you use the brakes to decelerate the car to a standstill the amount of kinetic energy that is transformed in that process is the same amount as it took to bring the car up to speed.

In both cases, acceleration and deceleration the, the same amount of work is done, the difference is the direction of energy transfer.

During acceleration (relative to the road) the kinetic energy of the car (relative to the road) is increasing

During deceleration (relative to the road) the kinetic energy of the car (relative to the road) is decreasing


In the case of an electric car:
During acceleration (relative to the road): potential energy stored in the battery pack is transferred to the motors, the spinning motors drive the wheels, the wheels grip the road and the car is accelerated (relative to the road).

During deceleration there is the option of regenerative braking. The wheels grip the road, the wheels drive the motors, the motors are acting as generators, generating electric energy, and the state of charge of the battery pack increases.

(In actual cars regenerative braking does not recover all of the kinetic energy, since there are losses at every intermediate step, but the regenerative braking is certainly worthwhile.)

I will start this answer with a general discussion, and then I will go to your question specifically.

There is the principle of relativity of inertial motion.

Example: let there be two trains, and they have a velocity relativity to each other. If you are a juggler, and you are performing inside a train carriage, can you tell from how the balls are moving on which train you are? You cannot; it feels the same. The only time you notice something is when the train undergoes a change of velocity.

A further implication of the principle of relativity of inertial motion is that while you can definitely tell when the train is changing velocity, whether you count that as an acceleration or a deceleration is arbitrary.

Whether you count a particular change of velocity as an acceleration or a deceleration follows from your choice of reference.

Of course, here on Earth the obvious choice is to use the entire Earth as reference of zero velocity. But the Earth has its daily rotation, and there is the motion of the Earth around the Sun, and there is the motion of our solar system around the center of mass of our Galaxy, etc.

My point is, distinction between acceleration and deceleration is not a measurable. What is measurable is how much change of velocity there is.



To your question specifically:

There is the amount of kinetic energy that must be transferred to an object in order to bring it up to a particular velocity $v$ relative to the reference coordinate system.

For a vehicle such as a car the obvious reference of velocity is the road. The speedometer of the car gives the velocity relative to the road.

There is the amount of kinetic energy that must be transferred to a car to bring it up to a particular velocity $v$.

Conversely, when you use the brakes to decelerate the car to a standstill the amount of kinetic energy that is transformed in that process is the same amount as it took to bring the car up to speed.

In both cases, acceleration and deceleration the, same amount of work is done, the difference is the direction of energy transfer.

During acceleration (relative to the road) the kinetic energy of the car (relative to the road) is increasing

During deceleration (relative to the road) the kinetic energy of the car (relative to the road) is decreasing


In the case of an electric car:
During acceleration (relative to the road): potential energy stored in the battery pack is transferred to the motors, the spinning motors drive the wheels, the wheels grip the road and the car is accelerated (relative to the road).

During deceleration there is the option of regenerative braking. The wheels grip the road, the wheels drive the motors, the motors are acting as generators, generating electric energy, and the state of charge of the battery pack increases.

(In actual cars regenerative braking does not recover all of the kinetic energy, since there are losses at every intermediate step, but the regenerative braking is certainly worthwhile.)

I will start this answer with a general discussion, and then I will go to your question specifically.

There is the principle of relativity of inertial motion.

Example: let there be two trains, and they have a velocity relativity to each other. If you are a juggler, and you are performing inside a train carriage, can you tell from how the balls are moving on which train you are? You cannot; it feels the same. The only time you notice something is when the train undergoes a change of velocity.

A further implication of the principle of relativity of inertial motion is that while you can definitely tell when the train is changing velocity, whether you count that as an acceleration or a deceleration is arbitrary.

Whether you count a particular change of velocity as an acceleration or a deceleration follows from your choice of reference.

Of course, here on Earth the obvious choice is to use the entire Earth as reference of zero velocity. But the Earth has its daily rotation, and there is the motion of the Earth around the Sun, and there is the motion of our solar system around the center of mass of our Galaxy, etc.

My point is, distinction between acceleration and deceleration is not a measurable. What is measurable is how much change of velocity there is.



To your question specifically:

There is the amount of kinetic energy that must be transferred to an object in order to bring it up to a particular velocity $v$ relative to the reference coordinate system.

For a vehicle such as a car the obvious reference of velocity is the road. The speedometer of the car gives the velocity relative to the road.

There is the amount of kinetic energy that must be transferred to a car to bring it up to a particular velocity $v$.

Conversely, when you use the brakes to decelerate the car to a standstill the amount of kinetic energy that is transformed in that process is the same amount as it took to bring the car up to speed.

In both cases, acceleration and deceleration, the same amount of work is done, the difference is the direction of energy transfer.

During acceleration (relative to the road) the kinetic energy of the car (relative to the road) is increasing

During deceleration (relative to the road) the kinetic energy of the car (relative to the road) is decreasing


In the case of an electric car:
During acceleration (relative to the road): potential energy stored in the battery pack is transferred to the motors, the spinning motors drive the wheels, the wheels grip the road and the car is accelerated (relative to the road).

During deceleration there is the option of regenerative braking. The wheels grip the road, the wheels drive the motors, the motors are acting as generators, generating electric energy, and the state of charge of the battery pack increases.

(In actual cars regenerative braking does not recover all of the kinetic energy, since there are losses at every intermediate step, but the regenerative braking is certainly worthwhile.)

Source Link
Cleonis
Cleonis
  • 22.5k
  • 1
  • 25
  • 66

I will start this answer with a general discussion, and then I will go to your question specifically.

There is the principle of relativity of inertial motion.

Example: let there be two trains, and they have a velocity relativity to each other. If you are a juggler, and you are performing inside a train carriage, can you tell from how the balls are moving on which train you are? You cannot; it feels the same. The only time you notice something is when the train undergoes a change of velocity.

A further implication of the principle of relativity of inertial motion is that while you can definitely tell when the train is changing velocity, whether you count that as an acceleration or a deceleration is arbitrary.

Whether you count a particular change of velocity as an acceleration or a deceleration follows from your choice of reference.

Of course, here on Earth the obvious choice is to use the entire Earth as reference of zero velocity. But the Earth has its daily rotation, and there is the motion of the Earth around the Sun, and there is the motion of our solar system around the center of mass of our Galaxy, etc.

My point is, distinction between acceleration and deceleration is not a measurable. What is measurable is how much change of velocity there is.



To your question specifically:

There is the amount of kinetic energy that must be transferred to an object in order to bring it up to a particular velocity $v$ relative to the reference coordinate system.

For a vehicle such as a car the obvious reference of velocity is the road. The speedometer of the car gives the velocity relative to the road.

There is the amount of kinetic energy that must be transferred to a car to bring it up to a particular velocity $v$.

Conversely, when you use the brakes to decelerate the car to a standstill the amount of kinetic energy that is transformed in that process is the same amount as it took to bring the car up to speed.

In both cases, acceleration and deceleration the, same amount of work is done, the difference is the direction of energy transfer.

During acceleration (relative to the road) the kinetic energy of the car (relative to the road) is increasing

During deceleration (relative to the road) the kinetic energy of the car (relative to the road) is decreasing


In the case of an electric car:
During acceleration (relative to the road): potential energy stored in the battery pack is transferred to the motors, the spinning motors drive the wheels, the wheels grip the road and the car is accelerated (relative to the road).

During deceleration there is the option of regenerative braking. The wheels grip the road, the wheels drive the motors, the motors are acting as generators, generating electric energy, and the state of charge of the battery pack increases.

(In actual cars regenerative braking does not recover all of the kinetic energy, since there are losses at every intermediate step, but the regenerative braking is certainly worthwhile.)