About this experiment
A straight position-time graph is the signature of constant velocity. Move a cart in either direction, change its starting position, and compare signed displacement with total distance. The graph and ruler use metres so that a steep line means a large speed, not a faster animation.
Learning goals
- Investigate how time affects position while controlling the other variables.
- Use the graph and numerical readings to test a prediction.
- Explain the physical assumptions and where this model stops applying.
How to use it
- 1Set the velocity to 6 m/s and the time to 4 s. Check that displacement is 24 m.
- 2Save a comparison curve, then reverse velocity. Explain the change in slope.
- 3Set velocity to zero and change initial position. Why is the line horizontal?
- 4Run the sweep and compare equal time intervals on the ruler.
The model
Assumptions
- The cart is a point mass on a straight track. Velocity is prescribed and stays constant.
- The ruler uses a fixed scale from -120 m to 120 m. Negative position describes the opposite side of the origin.
Try this in class
- Q1At -3 m/s for 8 s, what are displacement and distance?
- Q2Can position be negative while the cart moves to the right? Explain.
Frequently asked questions
Does negative velocity mean slowing down?
No. It indicates motion in the negative direction. Here the speed remains constant.
Why does changing the origin move the whole line?
Initial position adds the same offset at every time. It does not change the slope or displacement.