- #1

tobywashere

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## Homework Statement

I can solve this problem, but I keep getting a different answer from the textbook. I just want to confirm whether I'm wrong or the textbook is wrong.

A truck of mass 2.3 x 10

^{4}kg travelling at 15 m/s [51° S of W] collides with a second truck of mass 1.2 x 10

^{4}kg. The collision is completely inelastic. The trucks have a common velocity of 11 m/s [35° S of W] after the collision.

Determine the initial velocity of the less massive truck.

## Homework Equations

v`(m1 + m2) = v1m1 + v2m2

Cosine law

Sine law

## The Attempt at a Solution

P2

^{2}= 385000

^{2}+345000

^{2}-2(385000)(345000)cos16°

P2 = 109045

V = P2 / m2

V = 109045 / 1.2 x 10

^{4}

V = 9.1 m/s

This part of my answer is the same as the textbook's answer. It's the direction of the velocity that differs.

(sin16°)/109045= sinθ/385000

θ = 77°

Since the momentum of the lighter second truck is in the north west quadrant:

180° - (77° + 51°) = 53°

Therefore, the velocity of the second truck is 9.1 m/s [53° N of W]

The textbook says that the velocity is [26° N of W]

Can anyone check if this is right?