Physics homework-momentum and impulse-

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A user is seeking help with a physics homework problem involving momentum and impulse related to a collision between two cars. The first car (A) has a mass of 750 kg and is traveling at 30 m/s, while the second car (B) has a mass of 1600 kg and is moving at 20 m/s in the opposite direction. The user is asked to calculate the momentum of each car before the collision and determine the direction and speed of the combined wreck after the crash. A response suggests using the law of conservation of linear momentum and emphasizes the importance of using the correct signs for each momentum due to the opposite directions of travel. The user expresses a desire to learn rather than just find answers, indicating a commitment to understanding the material.
housedog1
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hello I'm struggling with physics this year at school i found this site looks great :smile: if this is a bad 1st post i won't be to surprised :biggrin: any way here's my problem...

Homework Statement



A Car A (with a mass of 750Kg) is travailing at 30 m s-1 and collides head on with car B travailing at 20 m s-1 with a (mass 1600kg) in the opposite direction


Homework Equations


A Calculate the magnitude of the momentum of each car before crashing

B If the two cars lock together in the crash, in which direction will they be moving immediately after the collision?

C
I Calculate the initial speed of the combined wreck immediately after the collision

II why dose the speed quickly reduce to zero?

The Attempt at a Solution



...ok so far i have drawn a picture like so...

(carA)----------------><---------(carB)
|750kg|-----|30ms-1|-------|20ms-1|--|1600kg|

lol i have no idea...also i have the answerers in the back of the book but that's not learning so that's why i came here :)

any help would be great! even if you could point me in the right direction

Thanks
housedog1
 
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use the law of conservation of linear momentum. Since the two cars are moving in the opposite direction, you have to use proper sign for each momentum.
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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