why force parallel to the axis of rotation do not make any torque.
What is the usual definition of a torque ?
is the tendency of force to rotate object around an axis .
or it's the cross product between the force and the distance vector .
Can you answer your own question now ? How can a force acting parallel to an axis tend to cause rotation about that axis ?
but way .
In the diagram :
A-A is the axis
B-C is a lever arm at right angles to the axis
Fa , Ft and Fr are axial , tangential and radial force components acting on the end of the lever arm at point C .
Which of the force components could cause rotation of the lever arm about axis A-A and which could not ?
i think Fr
can any one help me plz
No. Look at the diagram carefully.
Fr don't make torque becuase it is perpendicular to axis of rotation.
Fa i think
can any one help me
Ft wiil cause rotation about AA axis.....
Correct . Can you explain in words now why Ft does produce rotation about A-A axis and why Fa and Fr do not ?
Look t=r×f......the anlge btween r and fr is sin0=0...so torque is zero....no question for rotation.....
However fa will produce rotaion but the axis will be different....(an axis which is perpendicular to AA......BUT NOT ALONG AA)
So fa will rotate the object
Yes obviously fa will.....but as i said corresponding rotation axis will be different
Separate names with a comma.