Downloaded 29 times
More Related Content
Similar to Gravity, Friction, & More Forces In Everyday Life
Gravity, Friction, & More Forces In Everyday Life
- 1. Gravity, Friction, &More Forces in Everyday Life By Emmanuel Dikolelay
- 2. Introduction Everywhere we lookin our day-to-day lives, we see forces in action.
- 3. Gravity Gravity is notjust the force we see when objects fall to the ground, gravity affects all masses. Gravity is the force of attraction between all things that have mass. The strength of gravity depends on both the mass & the distance between masses. Larger masses have more gravity. Also, objects that are closer will always pull on you with more gravity. If gravity affects all objects, why aren't we pulled to a building when we walk past it? The force of gravity between objects on Earth is so tiny that we don't even feel it, especially when compared to the force of gravity from Earth itself. gravity: the attractive force between objects with mass
- 4. Gravity (con.) Gravity isalso what keeps the Earth in orbit around the sun. The sun has so much mass that it exerts a gravitational force on our entire solar system, keeping all of the planets, including Earth, in orbit.
- 5. Planets in Motion Whyaren't planets in orbit around the sun pulled toward it? Because, despite the sun´s gravity, the planets are also moving sideways. If you swing a yo-yo around your body, you are pulling it toward yourself by holding on to its string, that´s like the sun´s gravity, but the motion sideways keeps the yo-yo swinging around in the same circle.
- 6. Weight Weight is actuallya measure of gravitational force. Weight depends on both the force of gravity & the mass of the object. If you weigh two objects on a scale, the object with more mass will weigh more.
- 7. Weight (con.) Mass doesn´tdepend on location, but weight does because gravitational force can change depending on your location. For example, the force of gravity is less on the moon than it is on Earth. (The force of gravity depends on mass, & because the moon has less mass than the earth, it has a smaller gravitational force.) Therefore, the same object will weigh less on the moon than it will on Earth (about ⅙ as much).
- 8. Negative Acceleration Because gravitypulls you down towards the Earth, there is a constant acceleration toward the ground. The force of gravity on Earth is approximately 9.8 m/s(squ.). So, when you throw something up into the air, it gets slower until it stops in mid air, & then comes back down towards the Earth, accelerating down until it crashes into the ground. Also known as Negative Acceleration!
- 9. Friction Newton's first lawstates that an object in motion will remain in motion unless acted on by a net force. Try sliding your computer across the table. It slows down & eventually stops. So what is the net force that is affecting the book? Friction! It´s the force that opposes movement between touching surfaces & always acts against the direction of motion. When you ride a skateboard, the wheels slow down due to friction with the sidewalk & with the bearing in the wheels.
- 10. Friction (con.) In general,rougher surfaces have more friction. Sandpaper is harder to slide than normal paper because it has a rougher surface & therefore more friction. On the other hand, you can minimize the force of friction by greasing surfaces. Even our bodies have ways to reduce friction: We have fluid in our knees to reduce joint friction.
- 11. Types of Friction:Air Resistance There is also friction with air & water. The more technical term for friction with the air is air resistance. When you drop a feather, it floats from side to side because air resistance opposes the downward movement. Because friction is the force that opposes movement between surfaces in contact, objects with more surface area will have more air resistance.
- 12. Types of Friction Someother types of friction include:
- 13. Static Friction The forceof friction between surfaces not in motion. Static Friction is the result of molecules on one surface adhering to the other surface.
- 14. Sliding Friction Also knownas kinetic friction, the force of friction that affects surfaces in motion. When you are pushing a box, the force of friction that resists the motion is sliding friction. Because the surfaces aren't always bonded like they are in static friction, sliding friction is less powerful than static friction.
- 15. Rolling Friction The frictionbetween surfaces, when an object, such as a wheel or a ball, rolls freely over a surface. The friction between the wheels of a skateboard & the sidewalk is rolling friction. Rolling friction is weaker than sliding friction, which is why it is much easier to move something on wheels!
- 16. Terminal Velocity When anobject is falling to the ground, there are 2 forces acting on it: the force of gravity & the air resistance that is opposing the motion. When the air resistance equals the force of gravity on the object, there is no net force on the object, the forces are balanced. Without a net force, the object stops accelerating & it continues falling at a constant speed. Terminal Velocity is the speed at which the force of gravity equals air resistance. This speed depends on many factors, including the object's surface area, mass, how the object is oriented, & even the thickness of the air!
- 17. Magnetic Forces When youplay with magnets, you can feel either an attractive or a repelling force. A magnet is a material that is attracted to iron, steek, or other magnets. Magnets have a positive & negative end. Opposite charges attract & like charges repel. So, when you place a positive with a negative end, the magnetic forces pull together. If you try to touch a negative end with another negative end, or a positive with a positive, you will feel a repulsive force (they push each other away).
- 18. Electrical Forces Electrical Forcesare like magnetic forces in that they are caused by positive & negative charges in the matter. While magnetic forces are created by unmoving changes, electric forces are created by moving charges. The strength of both electric & magnetic forces is related to the amount of charge & the distance between charges. Electric & magnetic forces increase when the charge is stronger & when the charges are closer together.
- 19. Electromagnetism Electromagnetism is theinteraction of electric forces & magnetic fields, any electric charge in motion has a magnetic region around it. A wire that carries an electric current is surrounded by a magnetic field. You can make an electromagnet by wrapping a current-carrying wire around an iron core. Just like other magnets, one end is a north pole, & the other is a south pole.
- 20. Electromagnet Diagram The north& south ends of the bar are determined by the direction of the flow of electricity. If you reverse the flow, the charges reverse!
- 21. Centripetal Force Because velocityincludes both speed & direction, an object in circular motion is constantly changing its velocity, & therefore accelerating. Because an object in circular motion is accelerating, there must be an outside force acting on it (according to Newton's second law, force equals mass multiplied by acceleration). The force affecting an object in circular motion is called a centripetal force. A centripetal force always points towards the center of the circular path of motion.
- 22. Centripetal Force centripetal force:the force that causes an object to follow a curved or circular path & is directed inward, toward the center of rotation
- 23. Centripetal Force Examples Acentripetal force can be any number of things. The moon moves in a circular orbit around the Earth & is affected by the centripetal force of gravity. If you swing a yo-yo around in a circle, tension from the string is the centripetal force that keeps the yo-yo in circular motion.
- 24. Buoyancy & Density Theforce that keeps a rubber ducky floating is called the buoyant force. The buoyant force is an upward force exerted by a fluid onto an object that is immersed in the fluid. The buoyant force depends on the density of the fluid & the amount of fluid that the object displaces. The denser the fluid & the less fluid displaced, the stronger the buoyant force. The buoyant force is actually equal to the weight of the fluid that has been displaced, which is a principle called Archimedes´ Principle.
- 25. Buoyancy Example Don´t Forget:An object placed in a fluid will float if it is less dense than the fluid, & it will sink if it is denser than the fluid. https://jr.brainpop.com/science/forces/sinkorfloat/
- 26.
- 27.
- 28.