# torque definition

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#### theonlytycrane

##### Full Member
7+ Year Member

Using the equation rFsin(theta) is easy enough. But the previous definition (r cross F) confuses me. The cross product should result in a vector orthogonal to r and F. But in my see-saw drawing, the see-saw should torque down in the plane of r and F. The cross product makes it seems as though the see-saw would be torquing into or out of the page.

Am I missing something here?

#### aldol16

##### Full Member
5+ Year Member
The direction of torque is not the same thing as the direction of motion. The direction of torque is actually pointing along the axis of rotation and is given by a right-hand rule.

#### 7331poas

##### Full Member
5+ Year Member
The torque is into the page yes?

Sent from my iPhone using SDN mobile app

#### aldol16

##### Full Member
5+ Year Member
Yeah, if you're crossing r with F.

#### theonlytycrane

##### Full Member
7+ Year Member
The direction of torque is not the same thing as the direction of motion. The direction of torque is actually pointing along the axis of rotation and is given by a right-hand rule.

Does into or out of the page give any useful information about the torque? I guess in both cases the direction is along the axis of rotation, and is just a mathematical result from the definition of torque as a cross product.

#### aldol16

##### Full Member
5+ Year Member
It certainly gives some physical information about the torque - since torque is intimately related to angular momentum. However, I believe that would be outside the scope of the MCAT.