Newton’s Laws The Study of Dynamics

Isaac Newton Arguably the greatest scientific genius ever. Came up with 3 Laws of Motion to explain the observations and analyses of Galileo and Johannes Kepler. Discovered that white light was composed of many colors all mixed together. Invented new mathematical techniques such as calculus and binomial expansion theorem in his study of physics. Published his Laws in 1687 in the book Mathematical Principles of Natural Philosophy.

What is a Force? NO not THE Force A force is a push or pull on an object. It may be from gravity, electrical, magnetic, or muscle efforts. http://members.aol.com/PrinceG0R0/jedi.html

~Arise because of direct ~Gravity Contact Forces Field Forces ~Arise because of direct ~Gravity contact between objects. ~Electric Act over a distance. ex: friction, tension ~Magnetic

A net force causes an object to accelerate… To speed up To slow down To change direction

External Forces An external force is a force that acts on an object due to it’s environment. The net external force is the (vector) sum of all the forces acting on the body.

Newton’s First Law A body in motion stays in motion at constant velocity and a body at rest stays at rest unless acted upon by a net external force. This law is commonly referred to as the Law of Inertia.

Inertia Inertia is the tendency of an object to maintain its state of motion. The inertia of an object is proportional to it’s mass. Ex. A basketball in motion has more inertia than a tennis ball in motion.

Inertia Newton’s First Law explains inertia because when there are no unbalanced forces acting upon an object, the object will preserve it’s state of motion. Ex. A ball at rest on the ground doesn’t spontaneously move.

Ex: Newton’s 1st Law of Motion The small car acts (applies force) against the truck. Since the ladder was not latched, it had no other force acting on it, and it kept going http://www.geocities.com/Athens/Academy/9208/il.html

Implications of Newton’s 1st Law If there is zero net force on a body, it cannot accelerate, and therefore must move at constant velocity, which means it cannot turn, it cannot speed up, it cannot slow down.

What is Zero Net Force? SF = 0 The table pushes up on the book. FT A book rests on a table. Physics Gravity pulls down on the book. FG Even though there are forces on the book, they are balanced. Therefore, there is no net force on the book. SF = 0

Equilibrium An object is in equilibrium when the net external forces are zero. Objects that are either at rest or have a constant velocity are in equilibrium.

Free body diagram (FBD) Shows all the forces acting on an object. support force friction force Applied force weight

Diagrams Draw a force diagram and a free body diagram for a book sitting on a table. Physics N W Force Diagram N W Free Body Diagram