A point mass moving in the plane with an applied force. You can try to made the mass move in a circle and then see what happens when the force is suddenly removed, which will demonstrate Newton's first law (no net force implies motion at constant speed in a constant direction). Also observe which force directions cause the speed to increase or decrease.
Click and drag to impart a force on the particle.We call these bodies "rigid" because we assume that they do not deform under applied forces or moments.
A rigid body is an extended area of material that includes all the points inside it, and which moves so that the distances and angles between all its points remain constant. The location of a rigid body can be described by the position of one point \(P\) inside it, together with the rotation angle of the body (one angle in 2D, three angles in 3D).
location description | velocity description | |
---|---|---|
point mass | position vector \( \vec{r}_P \) | velocity vector \( \vec{ v}_P \) |
rigid body in 2D | position vector \( \vec{r}_P \) angle \( \theta \) | velocity vector \( \vec{v}_P \) angular velocity \( \omega \) |
rigid body in 3D | position vector \( \vec{r}_P \) angles \( \theta,\phi,\psi \) | velocity vector \( \vec{v}_P \) angular velocity vector \( \vec{\omega} \) |