This question is starting to annoy me?

Question

In a head-on accident involving a truck and a small parked car, investigators were able to determine that the small car's weight is 9904 newtons and that it was going 30.9 m/s after it was hit by the truck. They also determined that the truck was going 2.5 m/s after the accident.

The truck driver claimed that she wasn't going over 5 m/s when she hit the parked small car. If the mass of the truck is 38,000 kg, how fast (in m/s) was the truck going when it hit the small car?

Answer 1

3.322 m/s when she hit the car

Answer 2

...ya....wat tha people above me said...

Answer 3

Small car's weight = mg.     then, m of small car = weight / g

m = 9904 / 9.8 = 1010.61kg.

Now, im guessing this is a Conservation of Momentum question.

Let m1 = small car, m2 = truck,

v1 = speed of small car before collision (which is zero),

v1' (speed of car after collision) (which is 30.9 m/s) ,

v2 = speed of truck before collision (what we're trying to find),

v2' = speed of truck after collision (2.5m/s)

Then, m1v1 + m2v2 = m1v1' + m2v2'

0 + m2v2 = m1v1' + m2v2'

m2v2 = m1v1' + m2v2'

v2 = m1v1'/m2 + v2'

v2 = (1010.61 kg)(30.9m/s)/(38000kg) + (2.5m/s)

v2 = 0.8218 m/s + 2.5 m/s

v2 = 3.3218 m/s = 3.322 m/s

Thus, she was going at 3.322 m/s when she hit the car.