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Unit 3. Forces. 1. What is a force?. A force can cause a resting object to move, or it can accelerate a moving object by changing the object’s speed or direction. A force is a push or a pull Units of force is Newtons (N). Force is calculated using: F= ma F= force m= mass (kg)
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Unit 3 Forces
1. What is a force? • A force can cause a resting object to move, or it can accelerate a moving object by changing the object’s speed or direction. • A force is a push or a pull • Units of force is Newtons (N)
Force is calculated using: F= ma F= force m= mass (kg) a= accleration
2. Free body diagrams (FBD) • Show all the forces acting on a body • Forces are drawn from the center of mass
3. Combining Forces • Combine force arrows to show the result of how forces combine (known as the resultant) • Forces in the same direction add together • Forces in opposite direction subtract from one another • Net force is the overall forces acting on an object after all the forces are combined
Examples: • Adding forces: Push and pull on an object in the same direction • Subtracting forces: when two forces oppose each other
4. Balanced Forces • When the forces on an objects are balanced, the net force is zero and there is no change in the objects’ motion.
5. Unbalanced forces Wow, this one is not going to win a Nobel Prize • When an unbalanced force acts on an object • Speed up • Slow down • Change direction • Stop moving
6. List of forces • Weight (Fg): Force of gravity pulling down on an object • Fg=mg • Normal force (FN): Opposite of weight (Fg)
Applied Force (FA): any push or pull on the object • Frictional Force (Ff): force that opposes motion
Four types of Friction • Static: friction force that acts on objects that are not moving, acts in the direction opposite to the applied force • Sliding: opposes the direction of motion of an object as is slides over a surface
Video Watch • NSF Alpine Skiing