- #1

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## Homework Statement

## Homework Equations

xcxcxcxcxcxcxcxcxcxcxc[/B]

## The Attempt at a Solution

My attempt:

Let displacement of A be x m,

Let displacement of B be y m, and

Let displacement of C be z m.

Step2: [/B]a+b+c+d=(a+x-y)+(b+x)+c+(d+z)

2x-y=-z

Differentiating LHS and RHS components w.r.t dt:

d2x/dt - dy/dt = -dz/dt

2v

_{x}- v

_{y}= -v

_{z}

20-5=-z

15=-z

z= -15m/s (In upwards direction. Is this what the -ve sign means?)

Teacher's attempt:

**Let displacement of A be x m,**

Let displacement of B be y m, and

Let displacement of C be z m.

Let displacement of B be y m, and

Let displacement of C be z m.

**Step2:**a+b+c+d=(a+x-y)+(b+x-y)+c+(d+z)

0=2x-2y+z

Differentiating by dt on both sides:

2v

_{y}-2v

_{x}= v

_{z}

10-20=v

_{z}

-10=v

_{z}

v=-10m/s

Please tell why is my attempt wrong (In step two)

Thank you for reading.