1 / 14

Physics Talk 2.3

Physics Talk 2.3. Newton’s Second Law. Newton’s Second Law of Motion. Do Now: How did the mass on the car change the force needed to push it ?. L.O. Students use F=ma to solve problems relating to Newton’s Second Law of Motion S.C. Identify the forces acting on an object.

strom
Download Presentation

Physics Talk 2.3

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Physics Talk 2.3 Newton’s Second Law

  2. Newton’s Second Law of Motion • Do Now: How did the mass on the car change the force needed to push it? • L.O. Students use F=ma to solve problems relating to Newton’s Second Law of Motion • S.C. • Identify the forces acting on an object. • Determine when the forces on an object are either balanced or unbalanced. • Compare amounts of acceleration semi-quantitatively. • Apply Newton’s Second Law of Motion. • Apply the definition of the Newton as a unit of force

  3. Physics Talk 2.3 • What is the equation for Newton’s Second Law? • What does each variable represent? a = acceleration (m/s2) F = force (Newton – N) m = mass (kg)

  4. Physics Talk 2.3 • What is a Newton? • What causes acceleration? • The Newton is the unit for force. 1 N is the force required to make on kg of mass accelerate at 1m/s2 • 1N = 1 kg*m/s2 • Unbalanced forces

  5. Physics Talk 2.3 • What are some examples of Newton’s second law? • Does Newton’s 2nd Law ever stop working? • If you push a small cart with a large force, it will accelerate a great deal. If you use the same force on a car, it will accelerate less. • No, there is always acceleration, it just may be too small to measure.

  6. Sample Problem 1 • A tennis ball with mass 58g accelerates at 430m/s2when it is served. What is the force responsible for this acceleration? • Given: • m =58 g = 0.058 kg • a = 430m/s2 • Unknown: Force • Tool: F = ma • Solution: • F = 0.058kg*430m/s2 • F = 24.95 kg*m/s2 • F ≈ 25N

  7. Sample Problem 1 • Could an identical force accelerate a 5.0 kg bowling ball at the same rate? • Given: • F=25N • m = 5.0kg • Unknown: acceleration • Tool: F=ma • Solution: • 25N=5kg*a m/s2 • 25N/5kg= a

  8. Sample Problem 1 • Could an identical force accelerate a 5.0 kg bowling ball at the same rate? • No, an identical force would not accelerate the bowling ball at the same rate. • Solution: • 25N=5kg*a m/s2 • 25N/5kg = a

  9. Sample Problem 2 • A tennis racket hit a sand-filled tennis ball with a force of 4 N. While the 275 g ball is in contact with the racket, what is its acceleration? • Given: • F=4N • m=275g = 0.275 kg • Unknown: acceleration • Tool: F=ma • Solution: • 4N=0.275kg*a m/s2

  10. Gravity, Mass, Weight, and Newton’s Second Law • What is the acceleration due to gravity? • What does this mean about the force of gravity? • What is weight? • 9.8 m/s2 • If you drop a 1kg mass, there is a force of 9.8N acting on the object • The vertical, downward force exerted on a mass as a result of gravity

  11. Gravity, Mass, Weight, and Newton’s Second Law • How do you calculate an object’s weight? • What do the variables mean? w = weight m = mass in kg g = acceleration due to gravity (9.8 m/s2)

  12. Balanced and Unbalanced Forces • What is a free-body diagram? • If an object is not accelerating, what will the free-body diagram show? What if the object is accelerating? • A diagram showing the forces acting on an object • The diagram will show opposing forces that are balanced. If the object is accelerating, the opposing forces will be unbalanced.

  13. Free-Body Diagram • Example of free body diagram for

  14. Free-Body Diagram • Example of a free-body diagram for a car moving on the road at a constant velocity. • Is the car accelerating? Since the car is traveling at a constant speed, it is not accelerating. This means that the force of the road on the tires is equal to the air resistance and we have balanced forces.

More Related