Here are the issues my students thought about when they used the motion detectors to look at carts speeding up and slowing down on ramps:

- Is the position-time graph for an object going down a ramp starting at rest an exponential or a parabola?
- How can the slope of the velocity-time graph be negative when all the velocities we measured were positive?
- So, when the velocity is negative, the acceleration is always negative, right?
- So, when the object is moving in the negative direction, the acceleration is always negative, right?
- So, if the object is slowing down, the acceleration is always negative, right?
- So, if the velocity is decreasing, the acceleration is always negative, right?
- So, if velocity is a slope and acceleration is a slope, they have the same shape, right?