# Rollo World

**Prerequisite:** FreeFall

**Levels:** Challenge, Practice

**SpuCraft:** Balanced Balloons, High Balloons, Low Balloons, Retracting Arms, 2D Drone

In Drop and FreeFall, all the thrusters were connected to the same channel. Therefore, when you fired one thruster, you fired all of them.

Now you can fire the thrusters individually. This means that you apply forces to your spuCraft asymmetrically. This means that you can make it rotate or roll (on purpose).

#### Table of Links

#### Reference Sheets

[Coming Soon.]

Lots of stuff still needs to be added…

#### Rigid Body Kinematics: Calculating Angular Velocity & Angular Accceleration.

Rollo is a good place to practice applying rigid body kinematics relationships. Here is a good problem to work on that will help you solve the Swingline Challenge.

To help you with this problem, the video below shows how you can calculate angular acceleration using positions and accelerations of the two feet. In the video, we also derive an expression for angular velocity. However, as described in the second video, there are some problems with this velocity.

In the second video, we test the equations for angular acceleration and angular velocity within Rollo. In doing so, we discover a problem with the angular velocity. It is a problem that I am asking you to fix in this exercise.