Physics

• Projectile


  An object that is given an initial velocity and is then acted solely upon by gravitational force

  
• Projectile motion


  A form of motion where an object given an initial velocity is thrown or projected and is allowed to be acted on by gravity in a curved-like path

  
• Projectile motion


  • The object is given an initial velocity
  • The object is then acted solely upon by gravitational force
  • The object follows a curved-like path called a trajectory

  
• Projectile motion consists of two motions: horizontal and vertical

  
• Kinematic equations can be used to predict the unknown information about an object's motion in projectile motion

  
• An object in free-fall experiences an acceleration of -9.8m/s^2
• If an object is merely dropped, its initial velocity is 0 m/s
• If an object is projected upwards, its velocity is 0 m/s at the peak of its trajectory

  
• The velocity at which an object is projected upwards is equal in magnitude and opposite in sign to the velocity when it returns to the same height
• There are two types of projectile motion: horizontally launched projectiles and projectiles launched at an angle

  
• Horizontally launched projectiles


  1. The object is launched horizontally

  2. The horizontal velocity remains constant

  3. The vertical velocity changes due to gravity

  
• Projectiles launched at an angle

  1. The object is launched at an angle to the horizontal

  2. Both the horizontal and vertical velocities change due to gravity

  
• Situations involving projectile motion

  • Ball thrown by a man at the cliff
  • Sepak takraw player kicking a rattan ball
• Projectile motion has applications in various sports
• As the player kicks the rattan ball, you observed the motion of the rattan ball
• What will be your observations as you look into the motion of the ball on a strobe? Is it situation A or situation B? What do you think would be the explanation?

  
• Projectile


  Objects that move in projectile motion
• Trajectory


  The curved path followed by a projectile

  
• In projectile motion, the physical principles and mathematical formulas that must be applied are those concepts that were recalled earlier. Combining the two allows us to make predictions concerning projectile motion.

  
• Horizontally launched projectiles


  Projectiles that are launched with an initial velocity from an elevated position and follows a curved-like path to the ground
• Gravity is the natural force that causes objects to fall towards the earth. Hence, the acceleration due to gravity is always directed downwards and has a value of -9.8m/s2.
• Angle-launched projectiles


  Projectiles launched at an angle with respect to the horizontal and rises to a peak while moving horizontally. Upon reaching the peak, the projectile falls with a motion that is symmetrical to its path upwards to the peak.

  
• Parabola


  The pattern of an angle-launched projectile's trajectory motion

  
• Projectile motion consists of horizontal and vertical motion working independently.

  
• Situation 1: Free Kick!

  1. Illustrate the trajectory of the ball in order for Sam to get a goal

  2. Explain how you came up with that trajectory
• Situation 2: Throwing of Garbage


  1. Illustrate the trajectory to help Mat shoot his crumpled paper into the trash bin

  2. Explain how you ended up with that trajectory
• Sports/games that exhibit projectile motion

  • Volleyball
  • Shuttle cock
  • Soccer ball
  • Baseball hit by a bat
  • Pingpong ball
• Sports/games that do not exhibit projectile motion

  • Motorbike
  • Car racing
  • 100m dash
  • Dragonboat paddling race
  • Swimming
• Activity 1.3: World of Sports!


  1. List 5 different sports activities that can be considered to involve projectile motion

  2. Describe the way in which projectile motion is achieved in each sport

  
• Horizontal and vertical motions of a projectile are independent of each other

  
• As the rider takes off from the cliff

  Its downward vertical velocity is increasing due to the presence of gravity
• As the golf ball rises in the air

  Its vertical velocity (vy) decreases
• When the golf ball reaches the maximum height, its vertical velocity becomes zero
• When the golf ball returns to the ground

  Its vertical velocity will decrease
• In horizontally launched projectiles, the horizontal velocity (vx) is constant

  
• As the projectile ascends in an angle-launched projectile

  The upward vertical velocity (vy) is decreasing
• When the projectile reaches the maximum height in an angle-launched projectile, its vertical velocity is zero
• As the projectile descends in an angle-launched projectile, the magnitude of its vertical velocity is increasing
• The acceleration due to gravity is -9.8m/s2
• There is no external force acting on the horizontal motion of a projectile