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PHYSICAL SCIENCE

Learn about Newton's second law of motion, forces affecting objects, types of friction, and air resistance impact on falling objects.

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PHYSICAL SCIENCE

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  1. PHYSICAL SCIENCE Chapter 3 Forces 3.1 Newton’s Second Law

  2. 3.1 Newton’s Second Law Objectives • Define Newton’s second law of motion. • Apply Newton’s second law of motion. • Describe the three different types of friction. • Observe the effects of air resistance on falling objects.

  3. Force, Mass, and Acceleration • Newton’s first law of motion states that the motion of an object remains constant unless the object is subjected to an unbalanced force. • Newton’s second law of motion describes how the forces exerted on an object, its mass, and its acceleration are related.

  4. Newton’s Second Law • Newton’s second law of motion states that the acceleration of an object is in the same direction as the net force on the object, and that the acceleration can be calculated from the following equation: Acceleration (in meters/second2) = net force (in newtons) mass (in kilograms) a = Fnet m

  5. http://www.grc.nasa.gov/WWW/K-12/airplane/newton2.html

  6. Newton’s Second Law • Applying Math pg. 69. • Tennis Example: Tennis racket hits ball (making contact for only a few thousandths of a second) causing the ball’s velocity to change almost instantly. The ball’s acceleration could be as high as 5,000 m/s2 but its mass is only 0.06 kg. Fnet = ma = (0.06 kg)(5,000 m/s2) = 300 kg•m/s2 =300 N

  7. Friction • Friction is the force that opposes the sliding motion of two surfaces that are touching each other. • The amount of friction between two surfaces depends on two factors…. • kinds of surfaces (material) • force pressing surfaces together • The microscopic view of apparently smooth surfaces reveals that they have texture – dips, bumps, etc. • Where the two surfaces touch, welding or sticking occurs resulting in microwelds – the source of friction.

  8. Friction • The larger the force pushing two surfaces together, the stronger the microwelds will be. • Static friction is the frictional force that prevents two surfaces from sliding past each other. • Sliding friction is the frictional force that opposes the motion of two surfaces sliding past each other. • Rolling friction is the frictional force between a rolling object and the surface it rolls on.

  9. http://study.com/academy/lesson/what-is-friction-definition-formula-forces.htmlhttp://study.com/academy/lesson/what-is-friction-definition-formula-forces.html http://www.mrsciguy.com/Physics/Newton.html

  10. Air Resistance • Air resistance opposes the motion of objects that move through the air. • Without air resistance, all objects would fall with the same acceleration. • Air resistance acts in the opposite direction to the motion of an object through air. • The amount of air resistance on an object depends on the speed, size, and shape of the object.

  11. Air Resistance • As an object falls faster, the upward force of air resistance increases. • Eventually, the upward air resistance force becomes large enough to balance the downward force of gravity – making the net force on the object 0. • As a result, the object falls with a constant speed – terminal velocity. • Terminal velocity is the highest speed a falling object will reach. • Terminal velocity depends on the size, shape, and mass of the falling object.

  12. Video Links • Types of Friction - Animated Presentation (2:34) - https://youtu.be/UtdeKxyztSY • Misconceptions About Falling Objects (3:22) - https://youtu.be/_mCC-68LyZM • Hammer vs Feather - Physics on the Moon (1:22) - https://youtu.be/KDp1tiUsZw8

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