# Homework Help: How to calculate velocity from Mass and Force but no Time

1. Sep 4, 2016

### Scott Flood

[Mod note: Thread moved from General Math so no formatting template is shown]

I would like to calculate velocity based on the following set of facts:

A object of a known mass starts at rest and after a certain amount of time impacts into device that is able to measure its impact force. I would like to calculate the object's velocity. I am not able to measure the time it takes the object to travel this distance. The distance is a known length.

Last edited by a moderator: Sep 4, 2016
2. Sep 4, 2016

### Math_QED

I believe you posted in the wrong section. This is a physics problem.

3. Sep 4, 2016

### Stephen Tashi

What do you mean by "its impact force"? The force between two objects during a collision isn't likely to be a constant. A complete description of the force would be a graph of force as a function of time. Are you talking about a device that measures an average force during the collision? -or the maximum force during the collision ?

What distance do you mean by "this distance"?

4. Sep 4, 2016

### Staff: Mentor

I moved the thread to our homework section as it is homework-like.

More details about the impact measurement would help.

Knowing the distance is not useful.

5. Sep 5, 2016

### Scott Flood

Thank you for the questions regarding my post. The distance that I referenced is the distance from the point where the object is released at time zero to where it impacts with the device that measures the impact force. As for the force, I need to research the question you pose. As a practical matter, I am not sure how much variation the average force versus the maximum force will have on the calculated value for velocity. With any luck, the members of the Physics Forum will be able to help me work out a solution to this problem. Once I have a formula that provides a calculated value for velocity as the mass hits the impact point, based on the known value for mass and the distance traveled, I will be able to work out the methodology whether max force or average force should be used in the calculation. The core problem that I have is that I am not able to easily measure the time the mass travels across the known distance. Therefore, I am hopeful there is a way velocity can be calculated based on the known values of mass, distance and impact force. This is not a homework problem although it certainly could be. I have a small business and I am trying to work out this problem for a new product that I am contemplating. Thank you for your help.

6. Sep 5, 2016

### Scott Flood

The impact force would likely be seen as a decaying wave form that starts out with a maximum amplitude and then would rapidly decay to zero. I am working with sensor manufacturers to see if there is a impact force sensor that will work for this application.

7. Sep 5, 2016

### Nidum

What are you actually trying to do ?

8. Sep 5, 2016

### Scott Flood

Please feel free to move my inquiry to a different thread on the Physics Forums. I don't know where it should be placed. Unfortunately, I am not at liberty to share the ultimate requirement. This is one aspect of a larger problem.

9. Sep 5, 2016

### Stephen Tashi

My guess is that the object is being dropped, so "the distance" affects its final velocity when it collides with something. But instead of leaving people to guess, you should describe the experiment in a coherent manner.

10. Sep 5, 2016

### Scott Flood

Hello - The mass starts from a zero velocity and is "
The object is not dropped. Rather, the object is propelled horizontally from its initial position at rest to a final position where it impacts the force sensor. The mass of the object, the approximate distance the object travels and the impact force will be known values. I am trying to find a way to calculate the object's velocity without knowing the time it takes for the object to travel the given distance nor the value of the initial force that will be utilized to propel the object from rest to the impact point.

11. Sep 6, 2016

### Staff: Mentor

"the impact force" is not a useful number. If you can get the force as function of time, with sufficient resolution, you can work with that. The integral is related to the momentum.

12. Sep 6, 2016

### Nidum

There are so many unknowns in this problem that we are all guessing in the dark .

(1) Is this impact method really the only way to solve the problem ?

There are many other possible ways of finding velocities of moving objects .
There are many ways of measuring distances and elapsed times .

(2) If it is the only way then there are still many ways of doing it depending on what problem you are really trying to solve .

What is the object of the exercise ? - you need not tell us state secrets but please give us a bit more information to work with .

13. Sep 6, 2016

### Drakkith

Staff Emeritus
If you're developing a product then you need to hire a professional engineer or physicist to work with you. Especially if you cannot share your ultimate goal with us.

Thread locked for liability and safety reasons.