1 / 25

Newton’s Laws

Newton’s Laws. The Study of Dynamics. Isaac Newton. Arguably the greatest physical genius ever. Came up with 3 Laws of Motion to explain the observations and analyses of Galileo and Johannes Kepler. Invented Calculus.

zariel
Download Presentation

Newton’s Laws

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. Newton’s Laws The Study of Dynamics

  2. Isaac Newton • Arguably the greatest physical genius ever. • Came up with 3 Laws of Motion to explain the observations and analyses of Galileo and Johannes Kepler. • Invented Calculus. • Published his Laws in 1687 in the book Mathematical Principles of Natural Philosophy.

  3. What is Force? • A force is a push or pull on an object. • Forces cause an object to accelerate… • To speed up • To slow down • To change direction

  4. Newton’s First Law • The Law of Inertia. • A body in motion stays in motion at constant velocity and a body at rest stays at rest unless acted upon by an external force.

  5. A force diagram illustrating no net force

  6. A force diagram illustrating no net force

  7. A force diagram illustrating no net force

  8. A force diagram illustrating no net force

  9. Another example illustrating no net force

  10. Newton’s Second Law • A body accelerates when acted upon by a net external force. • The acceleration is proportional to the net force and is in the direction which the net force acts.

  11. Newton’s Second Law • ∑F = ma • where ∑F is the net force measured in Newtons (N) • m is mass (kg) • a is acceleration (m/s2)

  12. Units of force • Newton (SI system) • 1 N = 1 kg m /s2 • 1 N is the force required to accelerate a 1 kg mass at a rate of 1 m/s2

  13. Newton’s Third Law • For every action there exists an equal and opposite reaction. • If A exerts a force F on B, then B exerts an equal force of -F on A.

  14. FL FM 20 kg Working a Newton’s 2nd Law Problem Step 1:Draw the problem Larry pushes a 20 kg block horizontally on a frictionless floor with a force of 150 N while Moe pulls the same block horizontally with a force of 120 N. What is the acceleration of the block?

  15. N FL 20 kg FM FG Working a Newton’s 2nd Law Problem Step 2:Diagrams • Force diagram

  16. __________ _____+______ ___________ Working a Newton’s 2nd Law Problem Step 2:Diagrams contd FN • Free Body diagram FM FL FG

  17. Working a Newton’s 2nd Law Problem Step 3:Substitute • Make a list of givens from the word problem. • Mass of box = 20 kg • FL = 150 N • FM = 120 N • FL + FM = Total Force • Force Total = 270 N

  18. Working a Newton’s 2nd Law Problem Step 3:Solve Substitute in what you know. • F= m x a • Force Total = m x a • 270 N = 20 kg x a • F/m = a; 270 N /20 kg = a • 13.5 m/s2 = a

  19. Gravity as an accelerating force A very commonly used accelerating force is gravity. Here is gravity in action. The acceleration is g (10 m/s2).

  20. Gravity as an accelerating force In the absence of air resistance, gravity acts upon all objects by causing the same acceleration…g (10 m/s2)...

  21. Gravity as an accelerating force The pulley lets us use gravity as our accelerating force… but a lot slower than free fall. Acceleration here is a lot lower than g (10 m/s2)..

  22. The problem of weight Are weight and mass the same thing? • No. Weight can be defined as the force due to gravitation attraction. • W = mg = mass(kg) x (10 m/s2).

  23. N mg Flat surfaces – 1 D Force normal (N) is the common name given to any force opposing gravity for objects resting on horizontal surfaces. N = mg for objects resting on horizontal surfaces.

  24. Friction • The force that opposes a sliding motion. • Enables us to walk, drive a car, etc. • Due to microscopic irregularities in even the smoothest of surfaces.

  25. There are two types of friction • Static friction • exists before movement occurs • Kinetic friction • exists after movement occurs • Types • Rolling • Sliding • Fluid (Air & Water)

More Related