Transcript Forces
Forces Science of Technology © 2011 Project Lead The Way, Inc. Force The amount of force acting on an object can be determined if you know the distance traveled and the elapsed time. Data collected from trials is used to calculate velocity and acceleration. Gravity Sir Isaac Newton was a great scientist who is credited for discovering gravity. • One day Newton was sitting in an orchard under an apple tree and noticed apples falling to the ground. Maybe an apple hit him on the head; maybe it didn’t. Like all good scientists, Newton collected and examined the data (the apple) and ate it. • Why? Like all good scientists, Newton asked the question why? Why did the apple fall toward the ground instead of toward the sky? From this question Newton developed the Law of Gravity. Newton’s Law of Gravity • Gravity is the natural force that pulls one object toward another. The strength of this pull depends on the mass of the objects involved. • The pull is directly proportional to the masses of the objects and inversely proportional to the distance between the objects. • Because the earth is so large, objects are pulled toward its center instead of each other. This pull of gravity is what gives us weight and allows us to walk around without flying into space. Newton’s Laws After developing the law of gravity, Newton continued to work with objects of matter to determine how they react with each other. This work led him to the development of what is now called Newton’s 3 Laws of Motion Newton’s First Law of Motion The Law of Inertia Objects at rest stay at rest unless acted upon by an unbalanced force. Objects in motion stay in motion in a straight line and at a constant speed unless acted upon by an unbalanced force. Example: Cue ball striking a set of billiard balls Newton’s Second Law of Motion The Law of Acceleration Objects acted upon by an unbalanced force accelerate in the direction of the force directly proportional to the magnitude of the force and inversely proportional to the mass of the object. Example: Soccer ball that is passed and kicked into a goal by another player Newton’s Third Law of Motion The Law of Action and Reaction For every action by a force, there is an equal and opposite reaction by a different force. Example: Batter striking a ball that is pitched and hitting a home run Force • Force is the push or pull exerted on an object. • The magnitude of a force can be found by multiplying the mass and the acceleration of the object. • Force equals mass times acceleration. F = ma Image Resources Microsoft, Inc. (2009). Clip Art. Retrieved January 30, 2009, from http://office.microsoft.com/en-us/clipart/default.aspx