acceleration and terminal velocity

• Newton's laws surrounding forces were formulated hundreds of years ago, but are still used today - they help to describe the relationship between a body and the forces that act upon it
• Terminal velocity


  The maximum speed of an object, reached when the forces moving the object are balanced by its frictional forces
• Stages of an object falling through a fluid

  1. Object accelerates downwards due to gravity

  2. Frictional forces increase as speed increases

  3. Terminal velocity reached when weight is balanced by frictional forces
• The weight of an object does not change as it falls, as long as it stays whole
• Skydiver


  • Accelerates downwards initially due to gravity
  • Air resistance increases as speed increases
  • Eventually reaches terminal velocity when weight is balanced by air resistance
  • When parachute opens, air resistance increases and skydiver slows down to a new, lower terminal velocity
• As an object falls through a fluid

  Its acceleration decreases as the frictional force increases
• The object does not stop falling once its resultant force is zero, unless it has hit the ground
• Acceleration


  The rate of change in speed (or velocity) measured in metres per second squared
• Acceleration


  Change of velocity ÷ time taken
• Calculating average acceleration


  Final velocity (v) - Initial velocity (u) ÷ Time taken (t)
• If an object is slowing down, it is decelerating (and its acceleration has a negative value)
• Typical accelerations for different methods of travel

  • Running: 2 m/s²
  • Family car: 1-7 m/s²
  • Motorbike: 1-10 m/s²
  • Rollercoaster: 30-60 m/s²
  • Formula One car: 49 m/s²
• The acceleration in freefall due to the Earth's gravity is 10 m/s²