# Force acting on an object

1. Oct 28, 2015

### Karan Punjabi

Guys i want to ask if there is a object of a certain mass at rest and if another object of greater mass coming with a velocity will collide to it and will act a force on it and if there is another object with mass equal to the mass of the object at rest but the condition is one with greater mass and one with same mass has the same momentum then why they don't act the same force on the object at rest? Sorry for my bad grammar

2. Oct 28, 2015

### ZapperZ

Staff Emeritus
Your post not only have "bad grammar", but you need to learn to use proper punctuation and not produce run-on sentences. I mean, read it again from the perspective of someone who can't see what you are imagining in your head. Can you understand what you just wrote?

One of the things that you will learn in this forum is the art of communication via writing. It is also emphasized in the forum rules that you had agreed to. So this is a good time to learn. Repost your question and try to be as CLEAR as possible by putting yourself into the shoes of someone else who have no clue on what you are thinking of.

Zz.

3. Oct 28, 2015

### drvrm

i will advise you frame the question properly and then analyse it using the law of conservation of energy and momentum ? elaborate it say by assuming mass values and velocities . then say whether collision is elastic or inelastic etc.

4. Oct 28, 2015

### Karan Punjabi

A object x is at rest Case 1 that another object y with greater mass than object x is having a certain momentum collided with object x. Case 2 Object z having equal mass as the object x is coming with a momentum equal to object y and get collide to object x. Now my question is after both cases object x has different momentum but why the object y and z have same momentum. The collision is elastic.

5. Oct 28, 2015

### drvrm

i think you should write the pair of equations representing the conservation of momenta and energy and solve for the velocity of the particles after collision- this you will find in any inter level book say Resnick and Halliday's principles of physics /or even wikipedia .org on the net - and you will see interesting situations of exchange of momentum and energies constrained by the ratio of masses which are hitting each other.In case II of your question i have a hunch that the bodies are having same mass so they should exchange their momentum.

6. Oct 28, 2015

### Karan Punjabi

Yeah I have watched this @www.simbucket.com ... Its a website for simulation but thats not my question that what will be the velocities of objects after collision. I want to ask if object y and z have same momentum then why object x have different momentum in both cases?

7. Oct 28, 2015

### drvrm

When you write conservation of momentum and energy equations in the second case- you will find that incoming body and the static body have same mass ,so a perfect transfer of momentum will take place and the static one will take the velocity and the energy and will move on but in the first case that will not happen as masses are different. but one would have to write the equations and see for solutions-to get confidence on the results-that is how physics works -there is no shortcuts!

8. Oct 28, 2015

### Karan Punjabi

Ohk thankyou for the help

9. Oct 28, 2015

### IgorIGP

Karan Punjabi, the equality of moments does not mean the equality of interactions. The bodies of an equal momentumes and different velocities have different masses therefore they will interact differently. The rest is math of momentum and energy conservation laws.

10. Oct 28, 2015

### Karan Punjabi

Yeah I wanted this type of explanation but I'm not getting satisfied by this...different types of interaction depends on inertia correct ?

11. Oct 28, 2015

### IgorIGP

Yes. When the two bodies are interacting they are acting by the equal forces one to each other. At each time interval while they are in forced contact:
$F\cdot \Delta t= m \cdot \Delta v$
for each of a body (non relativistic case)
they interact synchronously so they have the same time $\Delta t$
the forces by the III Newton law are equal too
This means that while exchanging by the equal portions of momentum, they will have different velocity сhanges because they have different masses. It can be described as:
$m\cdot \Delta V = M\cdot \Delta u$

12. Oct 29, 2015

### Karan Punjabi

Got you.

13. Oct 29, 2015

### IgorIGP

Have you wished to say something like "Thank you, I caught it"?

14. Oct 29, 2015

### Karan Punjabi

Yes Thank you I caught it

15. Oct 29, 2015

### IgorIGP

You are welcome