Physics 151: Computerized Recitation #3

2-D Kinematics

This recitation will focus on projectile problems where the initial velocity is entirely in the horizontal direction. Please experiment with the four Physlet simulations below and complete the requested calculations on your worksheet.


Simulation 1: Horizontal Motion with Constant Velocity


The physlet above allows you to watch a ball moving horizontally for 8 seconds with a constant velocity that you specify. At time t = 0 the ball is at the origin of the coordinate system. Simply select a velocity between 3 and 20 in the input field directly below and click Simulate! to begin the animation.

Select Velocity (m/s):

Worksheet: Can you mathematically express the relationship between position and time?


Simulation 2: Freefall

The physlet below allows you to watch a ball falling under the influence of gravity (ay = -9.8 m/s2) where the initial velocity of the projectile is zero. At time t = 0 the ball is at the origin of the coordinate system and is at rest.



Click Simulate! to begin the animation.

Worksheet: Can you mathematically express the relationship between position and time?


Simulation 3: The Superposition of Horizontal and Vertical Motion

The physlet below allows you to watch the motion of three balls simultaneously. A red ball is moving horizontally with a constant velocity that you specify (for 8 seconds) as was the case for Simulation #1. A green ball has no horizonatal component of motion, but experiences an acceleration of ay = -9.8 m/s2 due to gravity as was the case in Simulation #2. A blue ball experiences both of these motions - a constant velocity in the horizontal direction and accelerated motion in the vertical direction.

Select a velocity and click Simulate! to watch the animation.

Select Velocity (m/s):

  • Run the simulation with several different values of velocity between 3 and 20 and study the motion of the three balls.
    • Can you notice any differences between the horizontal motion of the red and blue balls?
    • Can you notice any differences between the vertical motion of the green and blue balls?
    • Does the fact that the blue ball is moving horizontally affect its vertical motion in any way?
  • Can you relate the motion of one ball to the motion of the other balls?
    • Worksheet: For an initial horizontal velocity of 5 m/s -- how far has the red ball moved in 3.5 seconds? How far has the green ball fallen in 3.5 seconds? Use the simulation to check your answers.
    • Worksheet: How long does it take the green ball to fall 60 m? For an initial horizontal velocity of 12 m/s, how far does the red ball move during this time?



Simulation 4: Projectile Motion with Initial Horizontal Velocity

The physlet below allows you to simulate the trajectory of a ball with an initial horizontal velocity. At a time of 3 seconds the ball leaves the horizontal platform and then experiences an acceleration due to gravity. (However, the previous simulation has shown that the vertical component of motion does not have any effect on the horizontal component.) The simulation allows you to select different values of horizontal velocity and platform height. Select a Velocity and a Platform Height and click Simulate! to watch the animation.

Select Velocity (m/s): Enter Platform Height (m):

Suggestions for Exploration



Simulation 5: Minimum Velocity of Projectile Motion

Projectile