Chapter 12.2

Aristotle Ancient Greek Scientist Observations and logical reasoning provided scientific discoveries. Incorrectly proposed that force is required to keep an object moving at constant speed Held back the study of motion for thousand years

Galileo Italian scientist Experimented to find out about the world Studied how gravity produces constant acceleration Concluded that moving objects were not subjected to friction or any other force.

Newton Newton studied at Trinity college but were forced to leave. He built his ideas based on Galileo. He defined mass and force Introduced his laws of motion

Newton's First Law . Newton´s first law is often called the law of inertia Newton´s First Law of Motion states – An object at rest will remain at rest, or an object in motion will remain in motion in a straight line at constant speed, unless an external force is applied to it and changes its state motion

Newton's Second Law . The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass F=ma Force = mass x acceleration Units Force = Newtons or Kg m/s^2 Mass = kilograms Acceleration = m/s/s or m/s^2

Newton's Third Law .

Problem If an astronaut has a mass of 112 kilograms, what is his weight on Earth where the acceleration due to gravity is 9.8 m/s^2 ? Weight = Mass x Acceleration due to gravity = 112kg x 9.8 m/s^2 = 1100 kg*m/s^2 = 1100 N

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