forces more

• Static electricity


  Caused by the subatomic particles in an atom
• Subatomic particles


  • Protons
  • Neutrons
  • Electrons
• Protons


  Positive charge
• Neutrons


  Neutral (no charge)
• Electrons


  Negative charge
• When two different materials rub together some electrons can be transferred from one material to another. This creates a positive or negative charge on the surface of the object.
• If there are more electrons than protons then it will become negatively charged. If there are less electrons than protons then it becomes positively charged.
• Like charges repel - opposite attract
• The force between opposite charges is attractive. The force between like charges is repulsive.
• The force between objects is called an electrostatic force
• • If a material has more protons than electrons, it is positively charged.
  • If a material has more electrons than protons, it is negatively charged
  • If a material has equal amounts of protons and electrons, it is neutral.
• Electrostatics is the branch of physics concerned with electric charge at rest.
• When two objects have different charges, they will experience a force of attraction or repulsion depending on whether their charges are the same or opposite.
• • Most materials are neutral. 
  • But they can become charged by gaining or losing electrons.

  Gains electrons 🡪 becomes negatively charged

  Loses electrons 🡪 becomes positively charged
• • When neutral materials are rubbed together, electrons can move from one object to the other.
  • When a charged object touches a neutral object, electrons can move to the (more) positive object.
• • Magnetic force is strongest at a magnet's ends, or poles.
  • All magnets have a north and south pole.
• • A magnetic field is the area around a magnet where its magnetic force is felt
• The strength of the magnetic force depends on how close the magnets are to each other.
• • Only a few metals are magnetic:
  • Iron
  • Cobalt
  • Nickel
  • Some alloys are magnetic such as steel (contains iron)
• Earth has a magnetic field that surrounds it like an invisible bubble. The Earth’s North Pole is near Greenland and the South Pole is near Antarctica.
• Field lines show the direction of the magnetic force. They always point from the north pole to the south pole.
• • The Earth has its own magnetic field.
  • This magnetic field is how compasses work. The needle is magnetic.
  • Many scientists think this magnetic field is caused by the movement of molten iron in the Earth’s outer core creating electric currents.
• Electric fields


  Fields that can surround an object and exert forces on other objects within that area
• Magnetic fields


  Fields that can surround a magnet and exert forces on other magnets and certain types of metal
• Magnets


  • Can attract or repel each other without touching
  • Produce magnetic fields that can push or pull other magnets and certain types of metal
  • Do not attract all metals, but iron, nickel, cobalt, and steel are the most common examples of metals that are attracted by magnets
• Magnetic field


  • Causes like poles (north-north or south-south) of two magnets to repel each other
  • Causes opposite poles (north-south) of two magnets to attract each other
• Forces can act over a distance without touching
• We cannot directly see electric and magnetic fields, but we can map them out based on how they affect objects in the field
• Charging


  Objects become charged by rubbing against each other and transferring negatively charged electrons from one area to another
• Like charges (+/+ or -/-)


  Repel each other
• Balanced forces: Forces that are equal in size and opposite in direction,

  resulting in no change in motion.
• Unbalanced forces: Forces that are not equal, causing a change in the motion

  of an object.
• Unbalanced forces: Forces that are unequal in size and/or not opposite in direction, resulting in an acceleration.

  
• A stationary object on a table

  The force of gravity (9.8 N) is acting downward, but the force of the table (9.8 N) is acting upward, keeping the object stationary.
• A car accelerating


  The force of friction (10 N) opposes the force of the engine (50 N), resulting in an unbalanced force that causes the car to move forward.
• Two children playing tug-of-war

  Each child applies a force of 50 N to the rope, but in opposite directions, resulting in a balance of forces.
• Technologies that reduce force, such as shock absorbers in cars, cushioned

  shoes, and helmets.
• Crash Worthiness Technology


  The design and engineering of vehicles to minimize damage and injury in the event of a crash, using techniques such as crush zones, structural integrity, impact absorbing materials, and safety features.
• Benefits of Crash Worthiness Technology

  Reduced injury risk, increased vehicle durability, improved passenger comfort, enhanced safety, and compliance with safety regulations.
• Friction: A force that opposes motion between two surfaces in contact.

  Types of friction: Static, sliding, rolling, and fluid friction.