Chapter 4 Forces in One Dimension

1. Chapter 4 Forces in One Dimension

2. I. Force and Motion Force – push or pull exerted on an object. Forces cause an object to: Speed up Slow down Change positions Which results in a change in… acceleration B. Force (F) is a vector – represents size (magnitude) and direction. Force (F) – Just magnitude

3. object being manipulated System – External World – Everything around the system The hand & gravity are considered parts of the external world. II. Contact Forces and Field Forces An object from the external world makes contact with a system. Contact Force – Ex: holding a book pushing a book across a desk sitting in a chair B. Field Force – Forces that affect a system whether or not Earth is touching it. Ex: gravity magnetism

4. C. Agent – Cause of force applied to a system. Agent

5. III. Free-body Diagram Free-body diagram – Pictorial diagram that helps you identify all of the forces acting on a system Contact with the external world Fropeon ball FEarth’s mass on the ball System

6. Contact with the external world System Fhand on ball FEarth’s mass on ball

7. IV. Force & Acceleration What is the relationship between Force & Acceleration? Units for Force = kg · m/s2 = Newton (N)

8. V. Combining Forces Net Force – Resulting vector of combining forces. F1 = 5 N F2 = 5 N Fnet = 0 N

9. F2 = 10 N F1 = 5 N Fnet = 5 N

10. B. Newton’s Second Law – F = ma VI. Newton’s First Law An object at rest will remain at rest unless some unbalanced force acts on it. An object in motion will remain in motion unless some unbalanced force acts on it. 1. Newton’s first law is sometimes called the law of inertia. a. The tendency of an object to resist change.

11. Assignment: Practice Problems • Pg. 89, questions 1 – 5 1. A flowerpot fall freely from a windowsill. (ignore any forces due to air resistance.) System +y v a Fnet FEarth’s mass on flowerpot