What is the right hand screw rule in case of cross product?
What is the right hand screw rule in case of cross product?
The very standard rule for righthandedness of screws is to curl the fingers of your right hand around the screw with your thumb along it. If it screws in (in the direction of your thumb) when turned in the direction your fingers are pointing, it's righthanded.
The right hand rule for rotation vectors is based on the same idea: curl the fingers of your right hand in the direction of the rotation. If that's not easy, rotate your wrist until it's possible. Then the direction of your thumb is the direction of the rotation vector.
The version of the right hand rule that I recommend for cross products is more of the same: point flat-handed in the direction of the first vector and bend the fingers into the direction of the second vector. If that's not easy you might have to rotate your wrist until it's possible. Then your thumb will be pointing in the direction of the product.
The very standard rule for righthandedness of screws is to curl the fingers of your right hand around the screw with your thumb along it. If it screws in (in the direction of your thumb) when turned in the direction your fingers are pointing, it's righthanded.
The right hand rule for rotation vectors is based on the same idea: curl the fingers of your right hand in the direction of the rotation. If that's not easy, rotate your wrist until it's possible. Then the direction of your thumb is the direction of the rotation vector.
The version of the right hand rule that I recommend for cross products is more of the same: point flat-handed in the direction of the first vector and bend the fingers into the direction of the second vector. If that's not easy you might have to rotate your wrist until it's possible. Then your thumb will be pointing in the direction of the product.
