Science lesson 1: free-falling objects

• Uniformly Accelerated Motion (UAM)


  Uniform acceleration means a constant or a steady acceleration. Since acceleration is a vector quantity, uniform acceleration denotes that both the magnitude and the direction of acceleration stays constant.
• Uniformly Accelerated Motion


  • UAM occurs when an object experiences an increase or decrease in velocity at the same rate throughout the motion.
• When an object is moving at constant velocity, it means the speed is the same without speeding up or slowing down, and the direction is the same without turning.
• When an object is moving with uniform acceleration, the distances covered per second increase, the velocity increases by the same amount each second, and the acceleration is constant in both magnitude and direction.
• Negative acceleration is often called deceleration or retardation.
• The negative sign in acceleration only signifies direction, not magnitude.
• Free fall motion


  Any motion of an object or body solely influenced by gravity, where the effect of air resistance is negligible.
• On Earth, free fall is an idealization because there is always some air resistance that will also act on the object or body.
• The constant acceleration of a freely falling body is called acceleration due to gravity or free fall acceleration, denoted by the letter g.
• Earth's gravity always pulls downward, so the acceleration due to gravity is always downward and constant in magnitude and is independent of its speed.
• If the object is moving downward, the acceleration due to gravity makes it speed up, while the acceleration due to gravity makes the object slow down if the object is moving upward.
• Air resistance


  A frictional force that opposes the motion of a falling object. Its direction is always opposite to the direction of the object's motion.
• Air resistance increases with the speed of the object and the surface area of the falling object.
• Dropping a paper


  • A crumpled paper falls faster than a flat paper due to air resistance
• On Earth, it is not only gravity that affects a falling object but air resistance as well.
• A hammer falls faster than a feather on Earth due to air resistance, but on the Moon with no atmosphere, they fall at the same rate.
• Free fall equations


  Equations used to solve problems involving uniformly accelerated motion, where the acceleration is replaced by the acceleration due to gravity (g) and the displacement is in the vertical direction (y).
• Free fall equations


  • vf = vi + at
  • y = vi*t + 0.5*a*t^2
  • vf^2 = vi^2 + 2*a*y
• Free fall can be divided into three cases: 1) object dropped from rest, 2) object thrown downward, and 3) object thrown upward.
• Fall equations and the list of variables present in the equation

  • ✔ vf (final velocity in m/s)
  • ✔ vi (initial velocity in m/s)
  • ✔ t (time in s)
  • ✔ g (acceleration due to gravity in m/s2)
  • ✔ y (vertical displacement or distance in m)
• vf


  Final velocity in meter per second (m/s)
• vi


  Initial velocity in meter per second (m/s)
• t


  Time in seconds (s)
• g


  Acceleration due to gravity in meters per second squared (m/s2)
• y


  Vertical displacement or distance in meters (m)
• Objects dropped from a certain height were used as a common example for free fall motion
• Free fall can be divided into three cases
• Case 1: Object dropped from rest

  • Object experiences constant acceleration equal to g
  • Initial velocity is zero and considered to start from rest
• Case 2: Object thrown downward


  • Object has an initial velocity because it's given a push
  • Despite having an initial velocity, the object still experiences constant acceleration due to gravity
• Case 3: Object thrown upward

  • Velocity decreases as the object moves upward because gravity is slowing it down
  • At the maximum height, the velocity is zero for a split second before it starts to fall back down
  • As the object falls back down, it experiences the same acceleration due to gravity but its velocity is increasing because it's moving in the opposite direction (downward)
  • Velocity is positive when moving upward and negative when moving downward
• When you just drop something from a height without pushing or throwing it, it starts from rest, and it speeds up as it falls, with its speed increasing by the same amount every second
• Despite having an initial velocity, the object still experiences constant acceleration due to gravity. This means it continues to speed up as it falls, just like in Case 1
• At the maximum height where the object stops, its velocity is zero because it's reached the peak of its motion
• As the object starts to fall back down, it's still experiencing the same acceleration due to gravity. But this time, its velocity is increasing because it's moving in the opposite direction (downward)
• Remember that you must take the negative root because the direction of the velocity of the pen is downward. The velocity of the pen as it hits the ground is 9.90 m/s downward