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Ph i Review Physics R i What Are Newton's Laws of Motion? Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of Intel Corporation or its subsidiaries in the U.S. and other countries. *Other names and brands may be claimed as the property of others. Forces “Push or Pull” that acts between two bodies – – – – – – – Tension Gravitational force Frictional force Air resistance Electrostatic force Strong nuclear force Weak nuclear force Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of Intel Corporation or its subsidiaries in the U.S. and other countries. *Other names and brands may be claimed as the property of others. The SI unit for force is the Newton (N). This unit is equivalent to 1 kgm 2 s Phabulous Physics: Newton’s Laws N Newton’s ’ Fi First L Law “Law of Inertia” An object will continue in its state of motion unless compelled to change by a force impressed upon it it. What net force is required to maintain a 5000 kg object moving at a constant velocity of magnitude 7500 m/s? – Net force of 0 constant motion Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of Intel Corporation or its subsidiaries in the U.S. and other countries. *Other names and brands may be claimed as the property of others. Phabulous Physics: Newton’s Laws N Newton’s ’ Thi Thirdd Law L For every action, there is an equal, but opposite, reaction. Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of Intel Corporation or its subsidiaries in the U.S. and other countries. *Other names and brands may be claimed as the property of others. Phabulous Physics: Newton’s Laws W i h Weight The weight of an object is the gravitational force exerted on it by y Earth ((or whatever planetary mass the object is on). What is the mass of an object that weighs 500 N? Fw mg m Fw 500 N 51 kg m 9.8 s 2 g Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of Intel Corporation or its subsidiaries in the U.S. and other countries. *Other names and brands may be claimed as the property of others. Phabulous Physics: Newton’s Laws Oh E Other Examples l A book with a mass of 2 kg rests on a table. Find the magnitude g of the force exerted by the table on the book. FN Fg mg FN Fg 2 kg 9.8 sm2 20 N FN Fg Note: This force is called the Normal force because it acts perpendicular to the contact surface of the object. object Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of Intel Corporation or its subsidiaries in the U.S. and other countries. *Other names and brands may be claimed as the property of others. Phabulous Physics: Newton’s Laws Oh E Other Examples l A can of paint with a mass of 6 kg hangs from a rope. p If the can is to be pulled p upp to + a rooftop with a constant velocity of 1 m/s, direction what must the tension in the rope p be? FT FT Fg mg F T 6 kg 9 .8 sm2 59 N Fg Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of Intel Corporation or its subsidiaries in the U.S. and other countries. *Other names and brands may be claimed as the property of others. Phabulous Physics: Newton’s Laws Fi i Friction Friction is a contact force that is parallel to the contact surface and perpendicular to the normal force. force Static friction (Fs) occurs when a force tries unsuccessfully to set a body in motion. Kinetic (sliding) friction (Fk) occurs when a force acts on a body in motion. Generally Fs >Fk Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of Intel Corporation or its subsidiaries in the U.S. and other countries. *Other names and brands may be claimed as the property of others. Phabulous Physics: Newton’s Laws F i i Equations Friction E i Fs (max) s FN Fk k FN represents the coefficient of friction - a number that is related to the nature of the surfaces in contact with each other. Fs has a range of values dependent on the magnitude of the horizontal force being pp applied. Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of Intel Corporation or its subsidiaries in the U.S. and other countries. *Other names and brands may be claimed as the property of others. Phabulous Physics: Newton’s Laws F i i Problems Friction P bl A crate t off mass 20 kg k iis sliding lidi across a wooden floor. k between the crate and th fl the floor is i 0.3. 0 3 Determine D t i the th strength t th off the force acting on the crate. FN F k k FN k mg F k 0.3 20 kg 9.8 Fk F Fg m s2 59 N If the crate is being pulled by a force of 90 N (parallel to the floor), find the acceleration of the crate. Fnet F F f 90 N 59 N 31N Fnet Fnet 31N ma a 1.6 sm2 m 20kg Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of Intel Corporation or its subsidiaries in the U.S. and other countries. *Other names and brands may be claimed as the property of others. Phabulous Physics: Newton’s Laws F i i Problems Friction P bl A crate t off mass 100 kkg rests t on th the fl floor. s is 0.4. If a force of 250 N (parallel to th fl the floor)) is i applied li d to t the th crate, t what h t is i the th magnitude of Fs on the crate? s FN s mg F s, max FN m 100 kg 9 . 8 390 N F s, max 0.4 s2 Fs Fg F NOTE: Remember that Fs represents a range of values. In this case, the applied force of 250N iss less ess than thee maximum u Fs so thee actual cu magnitude of Fs is 250N. Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of Intel Corporation or its subsidiaries in the U.S. and other countries. *Other names and brands may be claimed as the property of others. Phabulous Physics: Newton’s Laws P ll Pulleys Pulleys are devices that change the direction of the tension force in cords that slide over them. In problems, problems we generally ignore the mass and friction associated with pulleys. Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of Intel Corporation or its subsidiaries in the U.S. and other countries. *Other names and brands may be claimed as the property of others. Phabulous Physics: Newton’s Laws I li d Planes Inclined Pl When a mass sits on an inclined plane, its weight g has two components: p normal and parallel to the plane. Weight mg mg cos Normal force mg sin Parallel force Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of Intel Corporation or its subsidiaries in the U.S. and other countries. *Other names and brands may be claimed as the property of others. Phabulous Physics: Newton’s Laws How do the laws of motion describe everyday events? Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of Intel Corporation or its subsidiaries in the U.S. and other countries. *Other names and brands may be claimed as the property of others. Phabulous Physics: Newton’s Laws Can the motion of any object be predicted? How? Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of Intel Corporation or its subsidiaries in the U.S. and other countries. *Other names and brands may be claimed as the property of others. Phabulous Physics: Newton’s Laws