'Moving About' Question :) (1 Viewer)

[HappyHour]

Hello,

Could someone please help and explain the following question to me:

"The diagram shows two cars each of mass 1000kg approaching each other. Car A is travelling at 15 m s^-1 and Car B approaches at 20 m s^-1."

If Car A rebounds at 10 m s^-1, what happens to car B?

a) Car B stops

b) Car B continues to move in the same direction at 5 m s^-1

c) Car B rebounds at 5 m s^-1

d) Car B also rebounds at 10 m s^-1

Thank you in advance.

 

[pikachu975]

Let car A move right and car B move left. Let car A moving right move in a positive direction and car B move in a negative direction.

m1u1 + m2u2 = m1v1 + m2v2
1000(15) + 1000(-20) = 1000(-10) + 1000 (v)
15 - 20 = -10 + v
v = 5

Since we have v as positive, it is moving to the right, as assumed from the start.

Answer: C

Since it's positive

 

[HappyHour]

Thanks!