Torque on a block with acceleration 4i-3j.

[chouZ]

Homework Statement

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:

Homework Equations

linear acceleration= (radius)(angular acceleration)

torque= (moment of Inertia)(angular acceleration)

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!...

 

[Hootenanny]

HINT: Definition of torque;

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

 

[Doc Al]

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

 

[chouZ]

thanks for the help guys...