Momentum,impulse, force question

1. Mar 28, 2013

study earth

Hi,

i have a question iv been working on for 4 hours and im soo confused.

My example is a bumper car in a elastic collision.

bumper car A travels at 3ms-1 east with a mass of 180kg
Bumper car B travels at 4ms-1 west witha mass of 200kgs.
the momentum before the collision is 1340kgms-1..this will be equal to momentum after the collision.

Car A travels at 1.5ms-1 after the collision int he opposite direction west
while Car B travels at 5.35ms-1 to the east.

what i need help with is change in momentum.

what is the change in momentum for both cars.

Δmomentum= F* T ( how am i supposed to get the average force for both cars)
the contact time was 2 secs but what is the change in momentum?

i dont get if its change in momentum for the whole system or just 1 car?

feel free to substitue any values for F or T etc..keep it simple as well (im only 16)

Thank you

2. Mar 28, 2013

voko

If there is no other force acting on cars A and B during the collision, then the total momentum of the A&B system does not change. This is "conservation of momentum". What may and usually does change is the momentum of each car.

3. Mar 28, 2013

study earth

hi thanks for that.
yes momentum for car a and b does change..
so can i get change in momentum for car A?
will it be final momentum (270Kgms-1 to west) - Inital momentum ( 540kgms-1 to the east)

4. Mar 28, 2013

study earth

what i dont get is how to calculate impulse when both Bumper car A and b collide...?
what force do i use?
what change in momentum do i use?
I know the Time?

Thank you

5. Mar 28, 2013

voko

In a fully elastic collision you have conservation of momentum and you have conservation of energy. Together they are a system of two equations for two unknowns that you then solve. Let $m_A$ and $m_B$ be the masses of the cars, and $v_{iA}, \ v_{iB}, \ v_{fA}, \ v_{fB}$ be their initial and final velocities. Conservation of momentum: $$m_A v_{iA} + m_B v_{iB} = m_A v_{fA} + m_B v_{fB}$$ Conservation of energy: $$\frac {m_A v_{iA}^2} {2} + \frac {m_B v_{iB}^2} {2} = \frac {m_A v_{fA}^2} {2} + \frac {m_B v_{fB}^2} {2}$$