Chapter 9

• Weight

  • Mass x gravitational field strength (10N)
  • amt of gravitational force acting on object
• Spreed

  • Distance(m)/time(s)
  • distance travelled per unit time
• Pressure

  • force/area(m^2)
  • amount of force per unit area
  • 1m^2= 10 000cm^2
• Work done

  • force x distance(m)
  • in J
  • transfer of energy through applied force on an object to make it move a distance in the direction of force
• Force is a push or pull interaction between objects that can result in a change n state of rest or motion.
• Frictional force occurs when two moving surfaces are in contact, which opposes its motion.
• Applied force produces a turning effect about a fixed point (pivot)
• Energy is the ability t do work or produce a change
• Contact forces

  • physical contact between two objects
  • friction
• Non-contact forces

  • do not require direct contact between object
  • Gravitational force, magnetic force, electrostatic force
• Frictional force

  • slows down moving object
  • produces heat
  • Good: holds nail in wall, walk, brakes
  • Bad: movement difficult, unwanted heat, wears away materials
  • Reduce: smooth surfaces, lubrication and streamlining the shape
• Electrostatic and magnetic force

  • unlike charges attract, like charges repel
• Measure gravitational force

  • spring balance
  • in extension, stretch when pulling force
  • in compression, compress when pushing force
• Mass and weight

  • Weight is amt of gravity acting on obj and mass is amt of matter in obj
  • (SI) Mass is kg, Weight is N
  • (Measure) Mass is electronic balance/beam balance, Weight is spring balance
• Work done and Energy

  • (Si) joule, J-> must be in metres
  • 3 conditions: force exerted, obj moves in direction of force
  • depends on force applied, distance moved
• Air pressure

  • go high, air pressure dec (likewise)
  • answer frame: air in _ dec/inc, air pressure dec/inc, atmospheric pressure outside is diff/same, atmospheric pressure forces/does not force __.
  • Airplane: pressure cause difficulty breathing, fly high where air pressure low, air pump to inc air pressure
• Liquid pressure

  • depth water inc, pressure inc
  • dam’s base thick, strong submarine material
• Pressure

  • when applied force inc/ contact area dec
  • in pascal (Pa)-> area must be in metre^2
  • answer: contact area big/small, weight distributed over small/big area of contact, larger/smaller pressure at__ (state what it causes)
• Speed

  • move stationary obj
  • change direction/speed
  • stop moving obj
• Turning effect

  • apply force on obj can produce turning effect about fixed point pivot
  • carry out action with minimal force (levers)
• Change in Size and shape

  • pumping air in balloon, squeezing sponge