Equal gaps or unequal gaps
Uniform and non-uniform motion in a straight line.
Three cars
Three cars start together. A friend notes where each car is at every second and measures the distance covered in each second.
What would the friend notice for a car moving at a steady speed?
What this lesson covers
The idea
An object moving in a straight line is in uniform motion if it covers equal distances in equal intervals of time (constant speed), and in non-uniform motion if it covers unequal distances in equal intervals.
Three cars
Three cars start together. A friend notes where each car is at every second and measures the distance covered in each second.
What would the friend notice for a car moving at a steady speed?
- The same distance in every second
- A longer distance in every next second
- A shorter distance in every next second
Three cars
Open each tab and read the distances covered in successive seconds.
Equal or unequal
All three cars moved in a straight line. Car A covered equal distances in equal intervals, so its speed stayed constant. Cars B and C covered unequal distances in equal intervals: B went faster and faster, C slower and slower.
An object moving in a straight line is in uniform motion if it covers equal distances in equal intervals of time (for all possible choices of time intervals), so its speed is constant. It is in non-uniform motion if it covers unequal distances in equal intervals of time.
Notes
Uniform motion: equal distances in equal intervals (constant speed). Non-uniform motion: unequal distances in equal intervals.
Check yourself
A car covers 5 m, 5 m, 5 m and 5 m in four successive seconds. Its motion is…
An object covers 3 m, 5 m and 7 m in three successive seconds. Its speed is…
Which describes non-uniform motion in a straight line?
A bus covers 14 m, 10 m, 6 m and 2 m in successive seconds. Its speed is…
- uniform — correct. Yes!
- non-uniform, with increasing speed. The distances are equal, so the speed is not increasing.
- non-uniform, with decreasing speed. The distances are equal, so the speed is not decreasing.
- constant. The distances in equal intervals are unequal, so the speed is not constant.
- increasing — correct. Yes!
- decreasing. The distances covered are getting larger, so the speed is not decreasing.
- Equal distances covered in equal intervals of time. That is uniform motion.
- Moving along a straight line. Uniform motion also takes place along a straight line, so this alone does not tell the two apart.
- Unequal distances covered in equal intervals of time — correct. Yes!
- decreasing — correct. Yes!
- increasing. The distances covered are getting smaller, so the speed is not increasing.
- constant. The distances are unequal, so the speed is not constant.