Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta
 You are Here: Home >< Physics

Mechanics - 2 objects collide travelling in the same direction watch

1. Can someone help me solving these types of problems?

You have 2 objects(A and B) at different masses travelling at 2 different speeds. They are travelling in the same direction. They then collide and move as a single object. F1 is the force B exerts on A, and F2 is the force A exerts on B.

Generally speaking, how would you find the values of F1 and F2?

Am I right in thinking that F1 and F2 are the same due to Newtons 3rd Law?
2. You need to think about the conservation of momentum laws which involve both velocity and mass.

So then they collide, which object will pass on its momentum to the other? It's a simple sum.

So now you have the momentum of both objects and their combined direction so rearrange the momentum formula to get the velocity of both.
3. (Original post by ThatPerson)
Can someone help me solving these types of problems?

You have 2 objects(A and B) at different masses travelling at 2 different speeds. They are travelling in the same direction. They then collide and move as a single object. F1 is the force B exerts on A, and F2 is the force A exerts on B.

Generally speaking, how would you find the values of F1 and F2?

Am I right in thinking that F1 and F2 are the same due to Newtons 3rd Law?
Why do you need to find the forces?
Generally speaking you don't know what these are unless you know the impact time dt of the collision. Then Fdt = change in momentum.
As this time is unknown you can't find the forces.
In these problems you are only interested in change in momentum, initial and final velocities, and kinetic energy. You solve them using mass, momentum and velocity. Not force.
4. (Original post by Stonebridge)
Why do you need to find the forces?
Generally speaking you don't know what these are unless you know the impact time dt of the collision. Then Fdt = change in momentum.
As this time is unknown you can't find the forces.
In these problems you are only interested in change in momentum, initial and final velocities, and kinetic energy. You solve them using mass, momentum and velocity. Not force.
I actually think that I've misread the question.

A hint/assumption given in the question is:

"F1 and F2 are not the magnitudes of the forces, remember, but the actual forces themselves."

So, what does this mean?
5. (Original post by ThatPerson)
I actually think that I've misread the question.

A hint/assumption given in the question is:

"F1 and F2 are not the magnitudes of the forces, remember, but the actual forces themselves."

So, what does this mean?
Forces are vectors. They have both magnitude and direction.
6. (Original post by joostan)
Forces are vectors. They have both magnitude and direction.
Oh.... So it is 1 and -1, hence the answer for my specific question is -1. :/ oops
7. (Original post by ThatPerson)
Oh.... So it is 1 and -1, hence the answer for my specific question is -1. :/ oops
Lol it happens all the time

Reply
Submit reply
Turn on thread page Beta
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: March 22, 2013
Today on TSR

Loughborough better than Cambridge

Loughborough at number one

Can I date a girl with no boobs?

Poll

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.