Kinematics of 1 D uniformly accelerated motion
1. In this applet, 'displacement' refers to that from the starting position.
2. The forward (upward) direction is taken to be positive.
3. When the option 'Edit vt graph' is chosen, the vt graph is capable to be changed by dragging the red points on the graph upward or downward.
4. The slope of displacementtime graph is velocity; the slope of velocitytime graph is acceleration. Uniform acceleration is the case when the acceleration is a constant, i.e. the velocity changes at a constant rate.
5. A straight vt graph means the acceleration is uniform. However, if the graph is composed of several straight lines of different slopes, the overall motion is no more described as uniformly accelerated.
6. Negative acceleration is usually called "deceleration". In fact, we need both the directions of velocity and acceleration to determine whether the object is speeding up or slowing down. The following table summarizes the cases
Velocity

Acceleration

Status

Positive

Positive

Real acceleration (speeding
up)

Positive

Negative

Real deceleration (slowing down)

Negative

Positive

Real deceleration (slowing down)

Negative

Negative

Real acceleration (speeding
up)

Example: