Force can be dened as that which changes, or tends to change, the state of rest, or uniform motion of a body. Force is a and therefore must be described using both . On Earth, force is dened as the product between the mass of an object and the acceleration due to gravity (9.8 m/s' ). So a 1 Kg mass exerts a downward force of 1 Kg x 9.8 m/s' or 9.8 Kg ' %/ . The unit of measure for force is called and is abbreviated as N. Therefore a 1 Kg mass exerts a force of 9.8 N downward. Often when looking at a problem involving forces, there are many forces acting on an object. It is useful to be able to look at a single force called which is the sum of all the forces working on the object. The process of nding the resultant of all the forces acting on an object is called the . If a single force that when applied to the object prevents any further motion than the object is said to be in . The net force on the object is the zero vector. Eg. 1: Two boys push a box to the east with forces of 30 N and 40 N respectively. What is the net force. At third boy decides to try and stop the box from moving and exerts a force of 55 N to the west. What is the net force. Eg.2: Two forces act on a large object. 500 N are used to pull the object south. 800 N are used to push the object on a bearing of 100. What is the resultant force? Resolving a Vector into Components In many situations involving forces, we are interested in a process that is the This process is called , Which means taking a single force and decomposing it into two components. Resolve vector } into its horizontal and vertical components. _, 0050 = 4 and sin0 = T f f \\t vmlcal axis Eg.3: A car is traveling at 80 km/h on a bearing of 260, draw a vector ; to represent the car's velocity and write the velocity in component form. Eg.4: A mass of 20 Kg is suspended from a ceiling by two ropes that make angles of 60 and 45" with the ceiling. Determine the tension in each of the ropes