for use with materialworlds Terminal velocity simulation
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Terminal velocity experiment 1
How does air friction affect a ball's fall?
Record how the velocity of a ball and the forces on it change as it falls - both with and without air friction.
Describe and explain how air friction changes the motion of the ball.
Terminal velocity experiment 2
How do changes in gravity, air friction, and its size and mass affect the ball's terminal velocity?
Investigate the effects of increasing each parameter in turn. How will it change the ball's terminal velocity and the time taken to reach it? Make a prediction then do the experiment.
Terminal velocity experiment 3 - Using the simulation to model a parachute jump
Open a parachute half-way through a skydiver's descent. What forces does the skydiver feel and what are their effects?
about the simulation...
A ball falls under the influence of gravity (a constant 10 N/Kg) and air friction (and the ground - when it hits it).
Arrows on the ball show forces (red arrows - with the triangle headed arrow showing the resultant force) and velocity (blue arrow). The simulation toolbar also shows the current simulation time.
A scrolling graph records how the vertical position, velocity and acceleration of the ball change with time. The ball's height above the ground is recorded as a positive distance, and an upward force or velocity would also be recorded as positive values. Conversely, a downward force or velocity are negative.
A bar displays the ball's kinetic (KE) and potential (PE) energy.
Controls allow gravity, air friction and the mass and size of the ball to be varied.
(Air friction in this simulation increases proprotionally to the surface area of the ball and also to the square of its velocity. The air friction control varies the constant of proportionality. The figure given for air friction is relative to its initial level - so a reading of 1.00 means unchanged; 0.5 means halved; 2.0 doubled)
Checkboxes provide the options of pausing the simulation every 0.2 seconds, and automatically when the ball hits the ground - useful for making detailed recordings and observations.
With the initial settings the ball reaches its terminal velocity before hitting the ground.
When the ball hits the ground it loses most of its kinetic energy in a fairly inelastic collision.
Should you want to allow the ball an uninterrupted fall you can delete the ground by pausing the simulation, selecting the ground plane with the mouse, and pressing the Delete key. (The ground will be replaced the next time you press
rewind.)Peculiarities...
The resultant force - as represented on the graph and as the triangle headed red arrow - has some averaging over time, and therefore sometimes changes less quickly than it really should.
The graphical "yposn" variable is measured from the centre of the ball - so that changing the size of the ball will mean that its rest position "on the ground" will be below (if smaller) or above (if larger) the graph's zero line.
The zero value for PE (potential energy) on the bar graph is measured relative to the PE of the ball resting on the ground - with the simulation having its initial settings. Any change in gravity, ball mass or size will change this "resting on the ground" PE.