3.  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: Nm We can also write torque as

4.  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.

5.  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/t oolss.htm

6.  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.

7.  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.

8.  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.

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

10.  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.

11.  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.

14.  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.

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

16.  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

17.  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

19.  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.