Question

A car with a mass of 1.1 × 103 kilograms hits a stationary truck with a mass of 2.3 × 103 kilograms from the rear end. The initial velocity of the car is +22.0 meters/second. After the collision the velocity of the car is -11.0 meters/second. What is the velocity of the truck after this elastic collision?

Answer 1

it is going to be conservation of momentum, and use the formula KE=mv^2 but I cant get the right answer! HELP!!!

Answer 2

you need to use only conservation of momentum and you will get the answer
make sure you use correct signs

Answer 3

So is that formula right? I keep getting answers that aren't options

Answer 4

+13 meters/second
+20 meters/second
+15.7 meters/second
+7.5 meters/second
+9.8 meters/second

THOSE are my options :/

Answer 5

solution: http://openstudy.com/study#/updates/535039a8e4b048ad9ac49fc9

Answer 6

Hmm, momentum is (mass x velocity)

initial momentum of car :
= (1.1 x 10^3 kg) x (22.0 m/sec)
= 2.42 x 10^4 kg•m / sec

final momentum of car :
= (1.1 x 10^3 kg) x (-11.0 m/sec)
= -1.21 x 10^4 kg•m / sec

so the car 'lost' the difference in energy
or (2.42 x 10^4 - 1.21 x 10^4)
= 1.21 x 10^4 kg•m / sec

This energy was transferred to the stationary truck, which means that the truck's momentum becomes

p = mv

or

1.21 x 10^4 kg•m / sec = (2.3 x 10^3 kg) * v

and rearranging that to solve for v gives

v = (1.21 x 10^4 kg•m / sec) / (2.3 x 10^3 kg)

≃ + 5.3 m/s