Physics - Distance-Time Graphs

What does a distance-time graph allow us to visualize?

How far something has traveled in a certain period of time.

What does the gradient of the line on a distance-time graph tell you?

The speed that the object is traveling at that time.

Why does gradient equal speed on a distance-time graph?

Because gradient = change in distance / change in time, which is the formula for speed.

If a cyclist travels 20 meters in 2 seconds, what is their speed?

10 meters per second (20 ÷ 2).

What does a straight line on a distance-time graph mean?

Constant speed.

What does a flat (horizontal) line on a distance-time graph mean?

The object is stationary (speed is zero).

What does a line that gets steeper on a distance-time graph show?

Acceleration (gradient and speed are increasing).

What does a line with a decreasing gradient on a distance-time graph show?

Deceleration.

How do you find the speed at a particular point on a curve (changing speed)?

Draw a tangent to the curve at that point, then calculate the gradient of that tangent.

What is a tangent?

A straight line that has exactly the same gradient as the curve at the point where they touch.

On a distance-time graph, what do straight lines, flat lines, and curved lines represent?

Straight lines = constant speeds, flat lines = stationary, curved lines = changing speeds.

If a point lies on a straight line, how do you calculate the speed?

Calculate the gradient of the line (change in distance ÷ change in time).

If a point lies on a curve, how do you calculate the speed?

Draw a tangent to the curve at that point, then calculate the gradient of the tangent.