Slide 1: Instituto Cumbres Jazmin Del Angel López Pérez 2° “A” Middle School Physic Mr. George Slide 2: Newton's first law is a restatement of what Galileo had already described and Newton gave credit to Galileo. However, a key difference between Galileo's idea and Aristotle's is that Galileo realized that force acting on a body determines acceleration, not velocity. This insight leads to Newton's First Law—no force means no acceleration, and hence the body will maintain its velocity. History of Newton’s first law Isaac Newton Galileo Galilei Aristotle Slide 3: The law of inertia apparently occurred to several different natural philosophers and scientists independently. The inertia of motion was described in the 3rd century BC by the Chinese philosopher Mo Tzu, and in the 11th century by the Muslim scientists Alhazen and Avicenna. The 17th century philosopher René Descartes also formulated the law, although he did not perform any experiments to confirm it.
The first law was understood philosophically well before Newton's publication of the law. History of Newton’s first law Mo Tzu René Descartes Alhazen Avicenna Newton’s first law of motion : Newton’s first law of motion Newton's first law is also called the law of inertia. Inertia is the resistance of mass, i.e. any physical object, to a change in its state of motion. It states that if the vector sum of all forces (that is, the net force) acting on an object is zero, then the acceleration of the object is zero and its velocity is constant. Examples Slide 5: Consequently:
An object that is not moving will not move until a force acts upon it.
An object that is moving will not change its velocity until a net force acts upon it. Examples Slide 6: The first point needs no comment, but the second seems to violate everyday experience. For example, a hockey puck sliding along ice does not move forever; rather, it slows and eventually comes to a stop. According to Newton's first law, the puck comes to a stop because of a net external force applied in the direction opposite to its motion. This net external force is due to a frictional force between the puck and the ice, as well as a frictional force between the puck and the air Examples A Laugh! Slide 7: Under these conditions the first law says that if an object is not pushed or pulled upon, its velocity will naturally remain constant
This also means that it will continue to remain motionless. Its velocity is constantly 0 m/s. Example 1 One force Examples Slide 8: Under these conditions we must realize that a group of forces on an object adds up so that all the forces appear to the object as one force. This one force that is the sum of all the forces is called the NET FORCE. The word net in this context means total. It is this net force that may change the velocity of the object. Example 2 Two or more forces Examples Slide 9: It is that property of matter, which opposes changes in velocity. Simply stated, an object will not change its velocity spontaneously. Something else must push on the object to speed it up, slow it down, or change its direction. Galileo’s explanation of inertia Examples Slide 10: Newton's first law of motion contains the same information as Galileo's explanation of inertia. Galileo stated: INERTIA is a property of matter. What did that sound like? Galileo Galilei Isaac Newton Slide 11: An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force. Conclution Unbalanced force Slide 12: Wikipedians ,(2008,13th October 2009),Newton’s laws of motion, 8th -10 -2009 at 05:00