What Are Newton's Laws of Motion?

Transcription

1 Phyic Review What Are Newton' Law of Motion? Intel Corporation or it ubidiarie in the U.S. and other countrie.

2 orce Puh or Pull that act between two bodie Tenion Gravitational force rictional force Air reitance Electrotatic force Strong nuclear force Weak nuclear force The SI unit for force i the Newton (N). Thi unit i equivalent to1 kgm 2 1

3 Newton irt Law Law of Inertia An object will continue in it tate of motion unle compelled to change by a force impreed upon it. What net force i required to maintain a 5000 kg object moving at a contant velocity of magnitude 7500 m/? Net force of 0 contant motion

4 Newton Third Law or every action, there i an equal, but oppoite, reaction.

5 Wih Weight The weight of an object i the gravitational force exerted on it by Earth (or whatever planetary ma the object i on). What i the ma of an object that weigh 500 N? w mg m g w N m 2 51 kg

6 Oh Other Example A book with a ma of 2 kg ret on a table. ind the magnitude of the force exerted by the table on the book. N g g g mg N m kg N N 2 2 Note: Thi force i called the Normal force becaue it act perpendicular to the contact urface of the object.

7 Oh Other Example + direction A can of paint with a ma of 6 kg hang from a rope. If the can i to be pulled up to a rooftop with a contant velocity of 1 m/, what mut the tenion in the rope be? g T T g mg m 6 kg N T 59

8 i rictioni riction i a contact force that i parallel to the contact urface and perpendicular to the normal force. Static friction ( ) occur when a force trie unuccefully to et a body in motion. Kinetic (liding) friction ( k ) occur when a force act on a body in motion. Generally > k

9 i riction i Equation k (max) k N N repreent the coefficient of friction -a number that i related to the nature of the urface in contact with each other. ha a range of value dependent on the magnitude of the horizontal force being applied.

10 N i riction i Problem A crate of ma 20 kg i liding acro a wooden floor. k between the crate and the floor i 0.3. Determine the trength th of the force acting on the crate. k k k N mg k m kg N crate. k 90N 59N 31N net ma f m 2 31 N 20kg 1.6 net m net 2 g a If the crate i being pulled by a force of 90 N (parallel to the floor), find the acceleration of the

11 N i riction i Problem A crate of ma 100 kg ret on the floor. i 0.4. If a force of 250 N (parallel to the floor) i applied to the crate, what i the magnitude of on the crate? mg, max, max N m 100kg N NOTE: Remember that repreent a range of value. In thi cae, the applied force of 250N i le than the maximum o the actual magnitude of i 250N. g

12 Pulley Pulley are device that change the direction of the tenion force in cord that lide over them. In problem, we generally ignore the ma and friction aociated with pulley.

13 Inclined dplane When a ma it on an inclined plane, it weight ha two component: normal and parallel to the plane. mg co Normal force Weight mg mg in Parallel force

14 How do the law of motion decribe everyday event?

15 Can the motion of any object be predicted? How?