# Homework Help: Torque on a block with acceleration 4i-3j.

1. Apr 7, 2007

### chouZ

1. The problem statement, all variables and given/known data
A 2.0-kg block starts from rest on the positive x axis 3.0 m from the origina and thereafter has an acceleration given by a = 4i-3j. The torque, relative to the origin acting on it at the end of 2.0 s is:

2. Relevant equations

linear acceleration= (radius)(angular acceleration)

torque= (moment of Inertia)(angular acceleration)

3. The attempt at a solution

I found the angular acceleration using the formula above
moment of Inertia=(mass)(radius square)
Then find the torque using the formula above

that's not it....help!...

2. Apr 7, 2007

### Hootenanny

Staff Emeritus
HINT: Definition of torque;

$$\tau = \vec{F}\times \vec{r} = m\vec{a}\times\vec{r}$$

3. Apr 7, 2007

### Staff: Mentor

Hint: Where is the block at the end of 2 seconds?

4. Apr 7, 2007

### chouZ

thanks for the help guys...

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