Quick answer: Average speed is the total distance an object travels divided by the total time it takes, written v = d ÷ t. This grade 6 science lab on average speed gives the aim, the equipment, the safety points, a step-by-step method, sample results and 7 analysis questions; the answers are on a separate page and the lab sheet is a free printable PDF.
Does a toy car keep the same speed over a longer distance? In this lab you time a car over four distances, calculate its speed each time and plot a distance-time graph to find out. You also judge how reaction time affects the accuracy of the results.
Level: Grade 6 science (Year 7 · Class 6) · Curriculum: MS-PS2-2
Aim
To measure the average speed of a toy car over several distances and to show that its distance-time graph is a straight line.
Equipment
- Toy car with free-running wheels
- Wooden board and two books to make a ramp
- Tape measure or metre rule (2 m or more)
- Masking tape for the marks
- Stopwatch (a phone timer is fine)
- Graph paper
Safety
Run the car on a clear, dry floor. Keep the track free of bags and cables so nobody trips, and stand to the side of the path of the car.
Method
- Build a ramp with the board and books, and mark the point where the car leaves the ramp as 0 m.
- Stick tape marks on the floor at 0.50 m, 1.00 m, 1.50 m and 2.00 m from the start line.
- Release the car from the same point on the ramp every time.
- Start the stopwatch when the front of the car crosses 0 m and stop it when it crosses the mark. Repeat three times for each distance.
- Calculate the mean time for each distance and record it in the table.
Results
Sample measurements from one group:
| Distance d (m) | Time 1 (s) | Time 2 (s) | Time 3 (s) | Mean time t (s) | Speed v = d ÷ t (m/s) |
|---|---|---|---|---|---|
| 0.50 | 1.31 | 1.28 | 1.34 | 1.31 | to calculate |
| 1.00 | 2.58 | 2.62 | 2.60 | 2.60 | to calculate |
| 1.50 | 3.95 | 3.91 | 3.99 | to calculate | to calculate |
| 2.00 | 5.20 | 5.28 | 5.24 | 5.24 | to calculate |
Analysis questions
Question 1 Mean time
Calculate the missing mean time for the distance 1.50 m.Question 2 Speeds
Calculate the speed for each distance, to three decimal places.Question 3 Graph
Plot a graph of distance (vertical axis) against mean time (horizontal axis) and describe its shape.Question 4 Gradient
Use the point (5.24 s, 2.00 m) and the origin to find the gradient. Compare it with the mean of the four speeds.Question 5 Timing error
The uncertainty in each time is about ±0.1 s because of reaction time. Calculate the percentage uncertainty for 1.31 s and for 5.24 s, and say which distance gives the better result.Question 6 Prediction
Use the speed 0.382 m/s to predict the time for the car to travel 3.00 m.Question 7 Improvements
Suggest two ways to make the measurements more reliable.
