Question 1
The table shows how the distance travelled by an object from its starting point changed with time.
| Time t (s) | 0 | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|---|
| Distance d (m) | 0 | 3 | 6 | 9 | 12 | 15 | 18 |
What is the object's speed, and is it uniform?
The right answer is the one marked above.
3 m s-1, uniform. The distance covered in every second is the same — 3 − 0 = 3 m, 6 − 3 = 3 m, 9 − 6 = 3 m, and so on.
speed = distance ÷ time = 18 m ÷ 6 s = 3 m s-1
Because the object covers the same distance in each successive second, we say it has a uniform speed, or constant speed. 18 m s-1 is the total distance, not the speed; and m s-2 is the unit of acceleration, not of speed.