High School Does acceleration affect impact energy vs constant velocity

[Ray033]

I do not have a good working knowledge of physics yet. I tried to piece this together but after researching this, I couldn’t figure out the correct laws of physics to combine to develop a formula to answer this question.

Ex. 1 - A moving object impacts a static object at a constant velocity.

Ex. 2 - A moving object impacts a static object at the same velocity but is accelerating at the moment of impact.

Assuming the mass of the objects is the same and the velocity at the moment of impact is the same in both examples.

Question - Does the acceleration component in example 2 increase the energy of the impact compared to the constant velocity used in example 1?

Any help in answering this question would be appreciated.

 

[PeroK]

Question - Does the acceleration component in example 2 increase the energy of the impact compared to the constant velocity used in example 1?

Any help in answering this question would be appreciated.

It depends whether the force producing the acceleration is maintained throughout the collision. For example, if you have a vertical pile driver, then the force of gravity continues to act while the object is being pile driven. And, indeed, you have to take this into account in your energy equations.

You might find a case where the accelerating force switches off at the moment of impact - and, in that case, the prior acceleration is irrelevant. In that case, only the speed at impact matters.

 

[Dale]

You might find a case where the accelerating force switches off at the moment of impact - and, in that case, the prior acceleration is irrelevant. In that case, only the speed at impact matters.

Or if the distance moved at the point of application of the external force is small, then the additional energy would be negligible.

 

[Ray033]

I do not have a good working knowledge of physics yet. I tried to piece this together but after researching this, I couldn’t figure out the correct laws of physics to combine to develop a formula to answer this question.

Ex. 1 - A moving object impacts a static object at a constant velocity.

Ex. 2 - A moving object impacts a static object at the same velocity but is accelerating at the moment of impact.

Assuming the mass of the objects is the same and the velocity at the moment of impact is the same in both examples.

Question - Does the acceleration component in example 2 increase the energy of the impact compared to the constant velocity used in example 1?

Any help in answering this question would be appreciated.

I do not have a good working knowledge of physics yet. I tried to piece this together but after researching this, I couldn’t figure out the correct laws of physics to combine to develop a formula to answer this question.

Ex. 1 - A moving object impacts a static object at a constant velocity.

Ex. 2 - A moving object impacts a static object at the same velocity but is accelerating at the moment of impact.

Assuming the mass of the objects is the same and the velocity at the moment of impact is the same in both examples.

Question - Does the acceleration component in example 2 increase the energy of the impact compared to the constant velocity used in example 1?

Any help in answering this question would be appreciated.

It depends whether the force producing the acceleration is maintained throughout the collision. For example, if you have a vertical pile driver, then the force of gravity continues to act while the object is being pile driven. And, indeed, you have to take this into account in your energy equations.

You might find a case where the accelerating force switches off at the moment of impact - and, in that case, the prior acceleration is irrelevant. In that case, only the speed at impact matters.

Thanks for the reply. So, acceleration can

I do not have a good working knowledge of physics yet. I tried to piece this together but after researching this, I couldn’t figure out the correct laws of physics to combine to develop a formula to answer this question.

Ex. 1 - A moving object impacts a static object at a constant velocity.

Ex. 2 - A moving object impacts a static object at the same velocity but is accelerating at the moment of impact.

Assuming the mass of the objects is the same and the velocity at the moment of impact is the same in both examples.

Question - Does the acceleration component in example 2 increase the energy of the impact compared to the constant velocity used in example 1?

Any help in answering this question would be appreciated.

It depends whether the force producing the acceleration is maintained throughout the collision. For example, if you have a vertical pile driver, then the force of gravity continues to act while the object is being pile driven. And, indeed, you have to take this into account in your energy equations.

You might find a case where the accelerating force switches off at the moment of impact - and, in that case, the prior acceleration is irrelevant. In that case, only the speed at impact matters.

Thanks for the reply. So, acceleration can increase the energy at the moment of impact vs constant velocity assuming that the force producing acceleration is maintained at impact. So, would I have to use the formula for kinetic energy and combine it with a formula from Newtons Laws of Motion to incorporate the acceleration into the calculation?

 

[PeroK]

Thanks for the reply. So, acceleration can


Thanks for the reply. So, acceleration can increase the energy at the moment of impact vs constant velocity assuming that the force producing acceleration is maintained at impact. So, would I have to use the formula for kinetic energy and combine it with a formula from Newtons Laws of Motion to incorporate the acceleration into the calculation?

That's a specific calculation for each problem. The impact in a particle collision is usually assumed to be of a sufficiently short time that the external forces are neglected during the collision itself. This allows you to use conservation of momentum and (for an elastic collision) conservation of kinetic energy to study the collision itself. The external accelerating force is applied to the particles before and after the collision, but not during it.

That said, you have to be careful that this is a reasonable assumption. And, you also have to keep an eye on how an external force like gravity may affect the solution to a collision problem.

 

[Ray033]

I really appreciate the reply. At this point, I was trying to test this in its simplest form and figure out how to calculate if acceleration could increase impact energy compared to constant velocity at impact. Just to give you an idea, I've changed my examples by adding basic values so I can try to eliminate any complicated variables when trying to figure out the calculations.

Ex. 1 - A 5 lb steel ball impacts a steel plate at a constant velocity of 1000 mph.

Ex. 2 – A 5 lb steel ball impacts a steel plate at 1000 mph but is accelerating 50 mph/sec at the moment of impact and the force producing the acceleration is maintained at the moment of impact.

Assuming the mass of the objects is the same and the velocity at the moment of impact is the same in both examples.

From what you told me earlier acceleration can increase impact energy compared to a constant velocity impact. Now I have to figure out the calculations to prove it.

I think your help has me pointed in the right direction.

Thanks again.