An object thrown or projected into the air is a projectile. To describe this motion fully, we need to know its position velocity acceleration If we know these 3 positions we can also predct what its motion will be in a time. Position, velocity and acceleration are all vectors. Each of these vectors can be resolved into two components at 90 degrees to it. Therefore, can analyse each component of the original vector seperately. Horizontal motion has no effect on vertiacal motion. Friction & Drag Friction The force that acts between two surfaces. The ammount of force used will increase the friction and the larger the surface area, the greater the friction. Drag Friction that occurs between an object and a liquid or gas. Gravity Wieght is proporitonal to mass. Weight = mass * acceleration due to gravity. Because the earth is flattened at the poles, gravity is not completely constant everywhere on earth. Gravity decresase by the square of the distance. Newton's First Law: An object will remain at rest or at uniform motion (constant velocity) unless acted upon by an external force. <100,0>Momentum Symbol: p <110,20>p = mv <20,35>m = mass of the body in kg v = velocity im ms^-1 p = momentum in kgms^-1 What does momentum mean? Momentum gained by an object equals the resultant or net force multiplied by the time for which it acts. ie when a force allererates a body from rest the momentum gained depends not only on the force but also on the time for which it acts. ALso the force X time(impulse) required to stop an object. In general, momentum change = force * time Why is momentum important? If Fnet external = 0 then the total momentum of the system remains constant (conservation of mass) Enables us to predict outcomes from starting conditions Many systems approach an isolated (closed) system Force