Car collision problem. Conservation of momentum

AI Thread Summary
In a car collision problem, a 1100 kg car traveling at 25.0 m/s collides with an 8200 kg truck moving at 20.0 m/s. After the collision, the car's velocity is 18.0 m/s. Participants emphasize the importance of applying the conservation of momentum to determine the truck's velocity post-collision. The initial kinetic energy of both vehicles must be calculated and compared to find the mechanical energy lost during the collision. Understanding these concepts is crucial for solving the problem accurately.
physicgeek
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A 1100 kg car traveling initially with a speed of 25.0 m/s in an easterly direction crashes into the rear end of a 8200 kg truck moving in the same direction at 20.0 m/s . The velocity of the car right after the collision is 18.0 m/s to the east.

1.How much mechanical energy is lost in the collision?



Thank you
 
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Hello physicgeek, you need to post your attempt at the problem before anyone at PF can help you as per the rules.
 
rock.freak667 said:
Hello physicgeek, you need to post your attempt at the problem before anyone at PF can help you as per the rules.

sorry I am new.

what i did was i took the kinetic energy of both and subtracted them.
but i got it wrong on webassign. (online homework)
 
physicgeek said:
sorry I am new.

what i did was i took the kinetic energy of both and subtracted them.
but i got it wrong on webassign. (online homework)

ah, I see. You forgot that that after the collision, the truck is still moving.

How would you go about finding the velocity of the truck? What law would you apply?

(Hint: it's in your thread title)

When you get that, find it for before the collision and after the collision and equate them.
 

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