topic p5- forces

• What's the difference between contact and non-contact forces?

  • contact= requires physical contact (e.g., frictional)
  • non-contact= acts without contact (e.g., gravity)
• how are weight, mass, and gravity related?

  • w= m X g:
  • weight (N)= force acting on an object due to gravity
  • mass (kg)= amount of 'stuff'
  • gravity (N/kg- 9.8 on earth)= gravitational field strength
  • gravitational force= the force of attraction between masses
• what's resultant force and work done?

  • resultant force= single combined force
  • work done= w=fXd (force X distance)
  • when a force moves an object through a distance, energy is transferred and work is done on the object
• force equation?

  • f= m X a :
  • force= mass (kg) X acceleration (m/s^2)
  • object=equilibrium= forces balanced
• what's hooke's law?

  • extension is directly proportional to force but this stops working when the force is great enough
  • f=kXe:
  • force= spring constant X extension (up to limit)
  • stretching, compressing or bending transfers energy
  • elastically deformed- tick
  • inelastically deformed- cross
• hooke's law graph shape?

  • Ee=1/2ke^2
  • straight line (proportional) until limit of proportionality
  • investigation of forces and extension= measure spring extension under different loads and plot a graph to find proportionality and spring constant
• definitions:

  • distance= total path (scalar)
  • displacement= shortest path (vector)
  • speed= how fast you're going
  • speed= distance/ time (scalar)
  • velocity= displacement/ time (vector)
  • velocity= speed in a given direction
• acceleration formula?

  • acceleration=proportional to the resultant force and inversely proportional to the mass of the object
  • a= triangle v/ t:
  • change in velocity/ time
• key features of graphs?

  • distance- time= gradient- speed
  • velocity-time= gradient- acceleration, area-distance
• what is terminal velocity?

  • large + less streamlined= lower- depends on shape + area
  • objects falling through fluids reach a terminal velocity
  • friction is always there to slow things down
  • drag increases as speed increases
  • constant velocity when drag= weight (no resultant force)
• summarize both of newton's laws

  • first= no change in motion without a resultant force
  • second= f=mXa (force= mass X acceleration)
• define inertia and the third law

  • inertia= resistance to motion change
  • third law= action= equal and opposite reaction- when two objects interact
• how to investigate motion?

  • investigates how mass + force affect acceleration
  • ticker timer= dot spacing shows speed, acceleration
  • light gates= measure speed and time
  • newton's second law explain the results