Is Acceleration Instantaneous? The Role of Time in Changing Forces

[tasveerk]

Homework Statement

In a scenario, the acceleration from 2-3 seconds is -2ft/sec^2 and from 3-4 seconds it is -1ft/sec^2. Does this mean that there was a moment between 2 and 4 seconds that the acceleration was -3/2 ft/sec^2?

Homework Equations

The Attempt at a Solution

 

[Andrew Mason]

Homework Statement

In a scenario, the acceleration from 2-3 seconds is -2ft/sec^2 and from 3-4 seconds it is -1ft/sec^2. Does this mean that there was a moment between 2 and 4 seconds that the acceleration was -3/2 ft/sec^2?

Not as the problem is given. But in real life the applied force cannot make an instantaneous change like that. The change can take place in a very short time, just not in no time. So there has to be a very brief moment around 3 seconds where the acceleration was -3/2 ft/sec^2.

AM

 

[ashishsinghal]

acceleration can change abruptly and there is no need for transitional stage. hence no.

I will give you an example. let's say that an iron cube is moving towards an electromagnet (switched off) and then it is switched on . The moment it is switched on a force attracts the iron. Since the force is instantaneous the acceleration is also instantaneous.

 

[tasveerk]

It seems as if we have two conflicting answers. Can anyone provide me with a source for their answer?

 

[Doc Al]

acceleration can change abruptly and there is no need for transitional stage. hence no.

I will give you an example. let's say that an iron cube is moving towards an electromagnet (switched off) and then it is switched on . The moment it is switched on a force attracts the iron. Since the force is instantaneous the acceleration is also instantaneous.

The force is not instantaneous. Neither is the change in acceleration.

(But you can pretend it is for the purpose of the problem.)

 

[ashishsinghal]

The force is not instantaneous. Neither is the change in acceleration.

(But you can pretend it is for the purpose of the problem.)

Then can you please explain what will happen when the electromagnet is switched on

 

[Doc Al]

Then can you please explain what will happen when the electromagnet is switched on

The point is that it takes time for the field to build up and time for the field to travel to the iron. Not much time, but time nonetheless. Few things happen 'instantly', although that's often a useful approximation.