Physics-forces

• Terminal Velocity


  The speed at which an object falling through a fluid (substance that can flow e.g. liquid/gas) reaches a constant speed in a steady direction
• Near the surface of the Earth, any object falling freely will have an acceleration of about 9.8 m/s^2
• Three Stages of Falling

  1. At start, object accelerates downwards due to force of gravity

  2. As speed increases, frictional forces such as air resistance or drag increase

  3. At terminal velocity, the weight of the object due to gravity is balanced by the frictional forces
• The weight of an object does not change as it falls
• Skydiver


  • Accelerates as they begin to fall
  • Speed increases as air resistance force increases
  • At terminal velocity, the air resistance force and weight are equal
  • Slows down when parachute opens, until new terminal velocity is reached
• Velocity-time graph for an object falling through a fluid

  1. Object accelerating downwards due to force of gravity
  2. Acceleration decreasing as frictional force acts against it
  3. Object reaches terminal velocity, no longer accelerating
  4. Object continues falling at terminal velocity
• Acceleration and force are directly proportional - as force doubles, acceleration also doubles
• Acceleration and mass are inversely proportional - as mass doubles, acceleration halves
• Required Practical: Investigating how force affects acceleration

  Set up air track with glider and hanging mass

  1. Use data logging software to calculate acceleration
  2. Release glider and record acceleration
  3. Repeat with different forces (0-1.3N)
  4. Calculate mean acceleration for each force
• Required Practical: Investigating how mass affects acceleration


  Set up apparatus as before

  1. Increase mass in 100g increments (0.98N)
  2. Record acceleration for each mass
• Independent variable


  The variable that is changed in an experiment
• Dependent variable


  The variable that is measured in an experiment
• Control variable


  The variable that is kept the same in an experiment
• Required Practical: Investigating the relationship between force and extension of a spring

  Secure a clamp stand and attach a spring

  1. Measure the unloaded length of the spring
  2. Add weights in 100g increments and measure the new length
  3. Repeat until 1000g total