Torque: the ability of a force to cause a body to rotate about a particular axis.

Torque is also written as:

Fl = Flsin = F l

Torque= force x lever arm

The SI unit for torque is: N•m

•We can also write torque as

An objects rotation depends not only on how much force is applied to it, but it also depends on where the force is applied.

The farther the force is from the axis of rotation, the easier it is to rotate the object, giving it more torque.

Torque also depends on the angle between a force and a lever arm.

A force does not have to be perpendicular to an object to make the object rotate.

http://www.aztecbolting.com/toolss.htm

The axis of rotation is a line, that the distance between any point on the line and any point of the body, remains constant under the rotation.

Image of Axis of Rotation.

A lever arm is the perpendicular distance from the axis of rotation to a a line drawn along the direction of the force.

A lever arm is also known as a moment arm.

Image of a lever arm.

Depending on the direction the force tends to rotate an abject, the torque will either be positive or negative.

In order to figure out the sign of a torque, imagine that it is the only torque acting on the object and that the object is free to rotate.

A point at which the object's mass can be assumed or for many purposes concentrated.

The center of mass is also the point at which all the mass of the body can be considered to be concentrated.

For regularly shaped objects, such as a sphere or a cube, the center of mass is at the geometric center of the object.

Moment of inertia is defined as the resistance of an object to changes in rotational motion.

Mass and Moment of inertia are both similar because they are both inertia. However, mass is an intrinsic property of an object and moment of inertia is not.

Equilibrium requires zero net force and zero net torque.

If the net force on an object is zero, the object is in translational equilibrium.

The second condition for equilibrium is the dependence of equilibrium on the absence of net torque.

Newton’s second law for rotating objects: Net torque = moment of inertia x angular acceleration

Rotating objects have angular momentum.

angular momentum = moment of inertia x angular speed

Translational and angular momentum:

translational:

momentum = mass x speed

rotational:

rotational momentum = moment of inertia x angular speed

Rotating objects have rotational kinetic energy.

Calculating rotational kinetic energy:

rotational kinetic energy = ½ x moment of inertia x (angular

speed)²

Translational and rotational kinetic energy.

Translational:

translational kinetic energy = ½ mass x (speed)²

Rotational:

rotational kinetic enery = ½ moment of inertia x (angular speed)²

The longer the input lever arm is compared with the output lever arm, the greater the mechanical advantage is.

Machines can alter the force and the distance moved.

The efficiency of a machine is a measure of how much input energy is lost compared with how much energy is used to perform work on an object.