Like my app ChanceLab, ForceLab is an exploratory environment for building a conceptual understanding of a relationship by playing around with it.

ForceLab lets you play with Newton's Second Law of motion,

F = ma,

by moving a space-walking astronaut with short bursts of gas, just as real astronauts do. Each burst gives the astronaut a little push left, right, up or down. You can see directly how the force causes an acceleration, or a change in velocity. Plus, it's fun!

Here's the physics of the situation: Each burst of gas exerts a total force F on the astronaut. According to Newton's 2nd Law,

F = ma

the force causes acceleration a, changing the astronaut's velocity v by a small amount dv in the direction of the force. The astronaut then moves in the direction of v', the new velocity .

Try some experiments. If the force F is always in one direction, the result is pretty easy to predict. But what happens if F and v are at an angle to each other?

That's when it's important to remember that F=ma is a vector relationship. The new velocity v' is the vector sum of the old velocity v and the velocity change dv as shown in the diagram.

Experimenting

Follow these steps.

• Drag the astronaut to a starting point that leaves room for your maneuvers.
• Touch the power button on the left side of the bottom bar to begin. The arrow buttons in the center are now active.
• Touch the arrow buttons to give the astronaut a push left, up, down or right. Each push changes the astronaut's velocity, shown as a yellow arrow.
• To run another experiment, touch the reset button on the right of the bottom bar.

These instructions are available in ForceLab by touching the "i" button in the top bar.

Settings

Touch the "gears" button in the top bar to adjust ForceLab's settings.