Copy of Unit 1_ Motion and it's interaction.pdf

Newton’s law of gravitational forces Unit 4 Newton’s Apple As the story goes, Newton was sitting under a tree and got hit in the head with a falling apple. He then began wondering more about gravitational force and how objects are attracted to Earth. The Universal Law of Gravit...

Newton’s law of gravitational forces Unit 4 Newton’s Apple As the story goes, Newton was sitting under a tree and got hit in the head with a falling apple. He then began wondering more about gravitational force and how objects are attracted to Earth. The Universal Law of Gravitation Every particle attracts every other particle in the universe with a certain force The force is directly proportional to the mass of the objects ○ As mass increases, force increases The force is inversely proportional to the distance between the objects ○ As distance increases, force decreases The Mathematical Representation G = the universal gravitational constant = 6.67 x 10-11 N*(m/kg)2 ○ Since this number is SO small, the forces between small masses are small enough to be ignored Since the distance term is squared, that means that it is more significant in the equation (distance affects the force more than the mass) So why do objects fall towards Earth? According to Newton’s 3rd Law, the forces exerted on each object is the same But objects accelerate towards the Earth at a MUCH greater rate because they have a MUCH smaller mass than the Earth If you think about F = ma, the forces are the same, but the masses are different Electrical and magnetic forces Unit 4 Electrical Forces Electrical forces are due to charges (positive or negative) and the forces of attraction or repulsion they exert on each other Similar to why an atom wants equal number of protons and electrons, charges are always in a state of wanting to be neutral Things can become charged by either gaining or losing electrons ○ For example, when you rub a balloon on your hair, the balloon is taking electrons off of your head. Your hair then repels itself because all of the strands are positively charged Coulomb’s Law The force exerted by two charges is directly proportional to the strength of the charges and inversely proportional to the distance between the two charges. Where k = 9 x 109 N*m2/C2 (C stands for Coulomb’s, a unit of charge) Does it look familiar? IT SHOULD!!! Because it’s the same as the Universal Law of Gravitation! Except it’s k instead of G. What’s different between G and k? Example Problem Two coins lie 1.5 meters apart on a table. They carry identical electric charges of -0.003 C. How much electrostatic force is produced between them? Remember k = 9x109 N*m2/C2 Magnetic Forces Magnetic forces occur due to the domains in an object becoming magnetized, or all facing the same way A common misconception is that magnets have a positive and a negative charge, but actually it works by magnetizing particles inside, like this Even if a magnet is cut in half, it becomes two smaller magnets Forces are applied to other magnets or certain metals that can be affected by a magnetic field What is similar about electric and magnetic forces? Electrical and magnetic forces both exert “force at a distance” which means they can apply a force on another object without direct contact Both electrical and magnetic forces are described as fields → a description of how the forces act on something that is nearby