Motion with constant acceleration review
|Kinematic variable||Variable that describes the motion of an object over time. Includes displacement , time interval , initial velocity , final velocity , and acceleration .|
|Kinematic formula||Formula that describes the relationships between kinematic variables when acceleration is constant.|
- is the
- is the
- is initial velocity
- is final velocity
- is acceleration
- Acceleration is constant over the time interval
Using the kinematic formulas
Choosing the best kinematic formula
Finding the known variables
Common mistakes and misconceptions
- People forget that some of the kinematic variables are vectors and can have negative signs. For example, if upward is assumed to be positive, then the acceleration due to gravity must be negative: . A missing negative sign is a very common mistake, so don't forget to check which direction is defined as positive!
- People forget that the kinematic variables we plug into a kinematic formula must be consistent with that time interval. In other words, the initial velocity has to be the velocity of the object at the initial position and start of the time interval . Similarly, the final velocity must be the velocity at the final position and end of the time interval .
- The second kinematic equation, , might require using the .