1 / 5

Newton’s Third Law of Motion

Weight is a force that is defined from the gravitational attraction between two masses. The gravitational force causes the less massive object to accelerate towards the more massive object.

zona
Télécharger la présentation

Newton’s Third Law of Motion

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. Weight is a force that is defined from the gravitational attraction between two masses. The gravitational force causes the less massive object to accelerate towards the more massive object. Near the surface of the Earth the acceleration due to gravity is considered constant, therefore we can directly relate mass and weight using this acceleration. This relationship assumes that the only force acting on the object is gravity. The object may actually have a different acceleration if there were other forces acting on it. Newton’s Third Law of Motion When an external force is applied to an object it means that there is an interaction between the two different objects. • Newton’s Third Law of Motion • For every action there is an equal but opposite reaction. • If two objects interact, the force F12 exerted by object 1 on object 2 is equal in magnitude and opposite in direction to the force F21 exerted by object 2 on object 1. This law requires you to examine the interaction between two objects! The action force is the applied force. The reaction force is the force due to the object resisting the imposed change.

  2. Example: A book rests on a table. What are all the action reaction force pairs for this situation? • The book pushes down on the table the table pushes up on the book. • The table pushes down on the Earth and the Earth pushes up on the table. • The attractive gravitational force between: • Earth and book, • Earth and table • and book and table. Earth When two objects are placed in contact and one is supporting the other the force perpendicular to the supporting surface is called the Normal Force. E.g.: The contact force the table exerts on the book, to support the book. A free body diagram is a diagram that show how all forces are applied to an object. This can include an outline of the object for forces applied at a specific location on the object, but we will be primarily considering forces applied to the object as a whole and therefore draw all forces from a point in the center of the object.

  3. Free-Body Diagrams

  4. Example: A 50 g hockey puck is sliding across a “frictionless” ice surface at a constant speed of 12 m/s. • Draw a free-body diagram showing all the forces acting on the hockey puck. • What acceleration is the hockey puck undergoing? • What is the magnitude of the normal Force? y a) x The velocity along each direction is constant, therefore the acceleration of the hockey puck is zero. b) c) 0

  5. Example: A child on a sled, with a combined mass of 40 kg, slides down a “frictionless” hill that makes an angle of 30o with respect to the horizontal. • a. Draw a free-body diagram of the forces acting on the child-sled system. • b. What is the magnitude of the normal force. • c. What is the magnitude of the child’s acceleration? b) c) 0

More Related