University:
Bradley University
Course:
PHY 100 | Fundamental Physics Concepts
Academic year:

2023
Views:

241

Pages:

24
Author:

Gudrunecg9m

D o c; D A SECTION 2 FRICTION • The force that 2 surfaces exert on each other when they rub against each other. • Sled moving across snow– bottom of sled rubs against snow surface (friction). Causes of Friction • Strength of friction depends on: 1. how hard the surfaces push together 2. Types of surfaces involved. Examples • Skiers- very little friction between snow and skis. Fast, smooth ride. • Reindeer have a hard time pulling skiers over sand. Harder, rougher surface– more friction, more force need. • Difference between rubbing hands together lightly or forcefully. FRICTION & MOTION • Friction acts in an opposite direction of the object’s motion. • Without friction, a moving object might not stop until it hits another object. TYPES OF FRICTION •1. Static Friction •2. Sliding Friction •3. Rolling Friction •4. Fluid Friction STATIC FRICTION • Friction that acts on objects that are NOT moving. • Need extra force to move stationary objects • Moving a Desk. n n • Occurs when 2 solid surfaces slide over each other. • Rubber brake pads pressing on bike wheels to make you stop. ROLLING FRICTION • Occurs when an object rolls over a surface. • Ex: Skateboarding- friction acts in the direction opposite of the skaters motion. D • Occurs when a solid object moves through a fluid. • Ex: surfer’s board cuts through the water. [ 1.Static friction allows objects to remain in place. 2.Allows moving objects to stop to avoid colliding with other objects. @ omvow • A force that pulls objects toward each other. • Newton concluded that a force acts to pull objects straight down toward the center of the earth. LAW OF UNIVERSAL GRAVITATION • Newton’s realization that the force of gravity acts between all objects in the universe. • Any 2 objects in universe are attracted to each other. Penpaper…. sownw ( 1. Mass2. Distance- • The amount of matter in an object. • More mass an object has, the greater its force. • SI unit for mass is Kilogram (km) • Everything that has mass is made up of matter. MASS • Sun is huge = applies a great force on all the planets which is why the planets revolve around the sun. • The farther apart 2 objects are, the lesser the gravitational force between them. • Less attraction as distance gets greater. WEIGHT VS MASS • Mass measures the amount of matter in an object. • Weight measures the amount of gravitational force exerting on an object. • Weight varies, Mass does not. FREEFALL • When gravity is only force acting on an object, object is in freefall. • Acceleration of object near earth’s surface is 9.8m/sec. (For every second falling velocity increases by 9.8m/sec.) AIR RESISTANCE • A type of fluid friction that an object experiences when falling through the air. • Friction- in opposite motion of object’s motion. AIR RESISTANCE • Falling objects with greater surface area experience more air resistance. • Leaf falls more slowly than acorn. 4 air resistance AIR RESISTANCE & VELOCITY • Air resistance increases with velocity. As a falling object speeds up, the force of air resistance becomes greater. • As object falls, velocity remains constant. TERMINAL VELOCITY • Greatest velocity a falling object reaches. • Reached when the force of air resistance equals the weight of object. PROJECTILE MOTION • Motion of an object that is thrown. • Gravity still acts on moving objects as well as stationary objects. • Gravity will pull it down. • Shoot arrow at bullseye, aim higher because gravity will start to pull it down.

Forces Section 2

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