A2L Item 086
- Description: Specify the characteristics of the linear acceleration of a body having uniform angular velocity.
- Goal: Hone angular kinematic quantities and distinguish them from linear kinematic quantities.
- Source: UMPERG
- Keywords: Acceleration, Angular Velocity, Mechanics, Rotational Motion
The question for students:
A mass moves in a circle with uniformly increasing angle.
As the angle θ increases, the linear acceleration of the mass has …
- constant magnitude and direction.
- constant magnitude, changing direction.
- changing magnitude, constant direction.
- both magnitude and direction changing.
Commentary for teachers:
Answer
(2) Students have a lot of difficulty reconciling linear kinematics with angular kinematics. Unless shown how to take derivatives in polar coordinates, or shown how to represent rotational kinematic quantities as vectors, students can only memorize specific relationships.
Some students may answer (1) thinking that ‘towards the center’ is a direction.