Transcript Force
I. Force A. Forces can cause a resting object to move, or accelerate a moving object by changing its speed or direction. B. A force is a push or pull acting on an object. I. Force C. Force is measured in Newton’s and are represented by an arrow that points in the direction of the force. II. Combining Forces A. Net force is the overall force acting on an object after all force are combined. B. Forces acting in the same direction are added together. II. Combining Forces C. Forces acting in opposite directions are subtracted. D. Balanced forces mean that there is no net force, no acceleration. (forces cancel out) II. Combining Forces Balanced forces means there is no change in motion. An object may move with a constant velocity if forces are balanced. II. Combining Forces E. Unbalanced forces means that a net force is present. Forces do not cancel out, and motion changes. ex. Losing tug of war II. Combining Forces F. When unbalanced forces are present the object will accelerate in the direction of the larger force. III. Friction A. Friction is a force that opposes motion B. The 4 main types of friction are: Static – keeps objects at rest Sliding – acts when sliding across a surface. Rolling – much less than sliding Fluid – friction with gases or liquids IV. Gravity A. Gravity is the force between any two masses. Gravity pulls objects together. B. The force of gravity causes objects to accelerate as they fall. C. Air resistance slows falling objects D. Terminal velocity is the fastest speed a falling object can reach. At terminal velocity the force of gravity is balances by the force of friction (air resistance). • When object reaches terminal velocity it continues to move with a constant velocity. Weight and Mass Mass is the amount of matter an object contains. An object’s mass does not change - no matter the location. The SI unit for mass is kilogram (kg) Weight and Mass Weight is the force that gravity exerts on an object due to its mass. The weight of an object is directly proportional to mass and the gravitational acceleration acting on the object. W=mg Weight and Mass Your weight will change based on gravity. Earth’s gravitational acceleration is 9.8 m/s2. The SI unit for weight is the Newton (N).