Difference between moment of force and force
Answers
Explanation:
The moment is a turning effect of force. The moment of force is about a fixed reference point. Moments of force is the measure of turning effects of a force about a point. A couple consist of two equal and opposite force acting with two different but parallel lines of action.
Explanation:
Before going to force and torque, you must understand difference between linear motion and angular motion as shown in figure.
Displacement in linear motion is in terms of distance such as meters etc. while displacement in angular motion is in terms of angle such as radians, degree etc.
Force: Whenever the tendency of force is to cause linear motion, its simply considered as force. Pushing a box on the floor is an example of force.
Torque: Whenever the force causes a rotational tendency, its known as torque. Since torque gives rotating tendencies therefore, there is always a center about which torque acts. Imagine opening a nut with a wrench as shown in the figure below. The center about which the torque is applied is the center of nut.
You must have observed that the force is still acting in linear fashion but it is the length of wrench which converts this linear tendency of force into rotational.
Therefore Torque = Force × length of wrench.
Greater the length of wrench greater is the torque. Therefore, for same force, torque can also be increased by increasing the length of wrench or any such length which is the distance between force applied and center. Therefore, its easier to open a tight nut by a long wrench.
Example: Inserting key inside the lock is applying force. Turning the key is applying torque.
Torque is known as moment of force. A moment of force is taken by multiplying the force by distance between the application of force and center of moment (just like length of wrench) as shown in above formula.
Couple: As the name suggests, its a combination of two torques as shown below.
Here, the center of rotation, or center of torque application is red dot. C is the force acting at both ends separated equally from center by distance l/2. So, total distance between the two forces is l. Now we calculate total torque due to these forces.
Torque due to top force T1=C×l2.
Torque due to bottom force T2=C×l2.
We can see that both the forces (up and down) tend to rotate the rod in anticlockwise direction about red dot. Therefore, both the torque will be added. This will give the value of couple.
Couple= T1+T2=C×l2+C×l2=C×l.