Motion

1
Motion
2
Speed Velocity

• Speed distance / time
• Velocity is speed but with a direction
• Whenever a measurement has a magnitude and
  direction, it is called a vector.
• Instantaneous vs. Average
• Instantaneous refers to the EXACT speed or
  velocity at a certain moment in time.
• Like a speedometer!
• Average refers to the speed calculated from a
  total distance traveled in a longer time
  interval.
• Average speed when traveling to school?

3
Acceleration

• Acceleration is the rate of change of velocity.
• Acceleration ? velocity / ? time
• Ex What is the acceleration of a car that goes
  0 to 30 m/s in 5 seconds?
• Ex What is the acceleration of a car that
  maintains 50 m/s of velocity for 10 seconds?
• What are the three controls in a car that can
  cause an acceleration?
• Can an acceleration be in the opposite direction
  of velocity?

4
Free Fall Activity

• Measure the acceleration of a ball dropped from
  rest.
• What do you need to measure?
• Results?

5
Free-Fall

• Ignoring air resistance (free-fall), objects will
  accelerate towards the ground at 9.8 m/s/s.
• This occurs whenever gravity is the only force
  acting on an object! (Going UP and DOWN!!)
• Gravity causes objects to accelerate UNIFORMLY!
• Many other accelerations we experience are not
  uniform.
• Exs?

6
Free-Fall - How fast

• A free-falling object gains 10 m/s (9.8 m/s) of
  velocity each second.
• Ex 1 A ball is dropped from rest. How fast is
  it going after 3 seconds? After 30 seconds?
• Ex 2 A ball is thrown downward at 25 m/s. How
  fast is it going after 3 seconds?
• Ex 3 A ball is thrown upward at 40 m/s. How
  fast is it going after 3 seconds? How fast after
  4 seconds? How fast after 6 seconds?

7
Free-Fall - How far

• The distance gained by a free-falling object is
  always increasing squarly proportional to the
  time, because the velocity of the object is
  always increasing.
• Ex 1 A ball is dropped from rest. How far does
  it fall in 3 seconds? 8 seconds? 10 seconds?
• Ex 2 A ball is thrown downward at 25 m/s. How
  far does it fall after 3 seconds?
• Ex 3 A ball is thrown upward at 100 m/s. How
  far away is it after 12 seconds?

8
Equations of Motion - Honors

• D ½ a t2 vo t
• Vf a t vo
• D Vf2 vo2
• 2 a