Science 6 Q3 all lessons

• Friction is the force that opposes motion between 2 surfaces touching each other
• Friction is less on smooth surfaces and more on rough surfaces
• Without friction, an object might move forever
• The 4 types of friction are:

  • Static friction: on objects that are not moving, requiring extra force to move
  • Sliding friction: when a surface slides over others
  • Rolling friction: when an object rolls, easier to overcome than sliding friction
  • Fluid friction: when a solid moves through a liquid, similar force to rolling friction
• Potential energy is energy stored not in motion, while kinetic energy is in motion
• Forms of energy include:

  • Mechanical
  • Chemical
  • Radiant/Light
  • Electrical
  • Sound
  • Thermal/Heat
  • Nuclear
  • Geothermal
  • Hydroelectric
  • Wind
  • Magnetic energy
• Mechanical energy can be kinetic or potential:

  • Kinetic when moving/moved
  • Potential when not in motion
• Chemical energy is stored in molecules, found in food from plants and animals
• Radiant/Light energy travels in empty space, like UV rays and X-rays
• Electrical energy is produced by moving electrons:

  • Static electricity: when 2 different materials are rubbed
  • Current electricity: when flowing
• Sound energy is produced by vibrating objects, like your throat when you speak
• Thermal/Heat energy is the motion of molecules, present in all bodies
• Nuclear energy is produced by nuclear fission
• Geothermal energy is from the Earth's core, Hydroelectric energy from a water wheel, Wind energy from windmills, and Magnetic energy when a magnet pulls metal objects
• Sound is produced in different ways. The simplest way is when objects hit each other. Sound produced this way come from the kinetic energy lost when moving bodies collide.
• All matter is made up of tiny particles in constant motion. Their constant movement produces energy. The sum of the energies from the moving molecules in an object is its thermal energy.

  This thermal energy can be transferred to another object. The energy transit is called heat. When heat is absorbed, it turns into thermal energy.
• Sound transmitted and heard because when the force of impact between two bodies and the vibrations of bodies cause the air molecules around them to vibrate.
• The vibrating air molecules pass on the energy to adjacent air molecules. In each of our ears, we have a very sensitive membrane called the eardrum.
• The vibrating air causes the eardrum to also vibrate. The small bones—hammer, anvil, and stirrup—then carry the energy to the brain through the auditory nerve.
• The energy from the movement of tiny particles will depend on how much heat was absorbed. A higher average energy from the movement of the particle also means a higher temperature. The heat flow is determined by temperature. Heat always moves from an object to an object of lower temperature. Heat flow will stop once the 2 objects are the same temperature.
• Energy from the sun reaches the earth in the form of radiant/light energy that travels by electromagnetic (EM) waves. The sun's energy travels as visible light, the only EM wave that can be seen by the naked eye. The sun also gives off other types of EM waves such as UV rays and infrared rays.
• Light energy can not move objects on its own. But it can be converted to another form of energy, like electrical energy, to make objects move and function. A solar radiometer, for example, absorbs light using a fanlike assembly in its glass bulb and converts it to kinetic energy.
• Safety precautions in using electricity:

  • Check all the wirings of your appliances and ensure their insulations are intact; if not, ask an electrician to repair them
  • Use appliances rated 220 volts (V) or use a transformer for appliances rated 110 V
  • Avoid octopus connections and adapters with too many plugs
  • Do not attempt to repair appliances yourself
  • Keep appliances away from water and avoid touching them with wet hands
  • In case of power trips or blown fuses, locate the cause before turning it on again
• Tips for efficient use of electricity:

  • Turn off lights and appliances not in use
  • Look out for leaks in your fridge or air conditioned rooms as they can cause more electricity to be consumed
  • When the food on the stove is boiling, set it to low or off
  • When ironing the last few pieces of clothes, set it to low or even turn it off
  • When using the washing machine, put in a moderate number of clothes in 1 load
  • When buying appliances, consider the efficiency ratings and other energy-saving features, even if they cost more initially, they save money in the long run
  • Monitor your electricity consumption and inform your parents if the bill suddenly goes up
• There are 6 simple machines: the lever, wheel and axle, inclined plane, wedge, screw, and pulley. The common thing about them is that they make our tasks easier.
• A lever is a straight or curved rigid bar that is free to turn about a fixed point
• All levers have 3 locations of interest:

  • The fulcrum / fixed point
  • The point of effort / where work is done on the lever
  • The load / the one being moved
• A lever multiplies the effort force, creating a larger output force that acts on the load
• The multiplied amount of load depends on the distances of the point of effort and the load from the fulcrum
• The distance from the fulcrum to the load is called a resistance arm
• The distance from the fulcrum to the point of effort is called the effort arm
• In any lever, the effort is less whenever its distance from the fulcrum and the distance from the fulcrum is increased, and the distance of the load from the fulcrum is decreased
• By pushing farthest away from the fulcrum, less effort is needed to lift the load
• The effort needed is further reduced if the load is placed nearer to the fulcrum
• Mechanical Advantage equates to the Output Force divided by the Input Force
• Classes of Levers:

  Class 1 Lever: fulcrum is located between effort and load. The effort and resistance move in opposite directions. Ex: crowbars, scissors, and pliers.

  Class 2 Lever: has the load between effort and fulcrum. The effort and resistance move at the same direction. Ex: wheelbarrow, bottle opener, and nutcracker.

  Class 3 Lever: has the effort between the load and fulcrum. Effort and resistance move in the same direction. Ex: fishing rod, tweezers, and tongs.
• A pulley is a grooved wheel that turns around an axle which is held in place by a mounting bracket. A rope or wire moves along the wheel's circumference. It is used to pull up objects. Like a lever, a pulley has 3 points of interest. The fulcrum, point of effort at one end of the rope, and the resistance or load to be lifted.
• Types of pulleys:

  • Fixed pulley: axle fixed on a surface, fulcrum at the center of the axle, does not move, does not increase magnitude, speed, or distance of the force. Ex: flagpoles, clotheslines
  • Movable pulley: moves along the rope or wire, fulcrum at the edge of the wheel, load at the middle of the axle, effort at one end of the rope, increases the magnitude of the force but decreases its distance. Ex: ziplines, weight machines, elevator cables
  • Compound pulley: combination of 2 or more fixed and movable pulleys, fixed pulleys change the direction of the force, movable ones lessen the effort needed to lift it. Ex: ships, billboards
• An inclined plane is a plane tilted at an angle, with one end higher than the other. It makes moving things to a higher place a lot easier. On a less steep ramp, less force is needed. However, the incline will be shorter. Ex: wheelchair ramp
• A screw hook is preferred over a nail for hanging a picture as it can be easily removed and put back in the same hole without damaging the wall