The slope of a speed-time graph represents the rate of change of speed with respect to time. In physics, this rate of change of speed with time is defined as acceleration. Thus, the correct answer is:
○ acceleration
To elaborate, let's consider what each of the options means in the context of a speed-time graph:
- Speed: This is what the graph is plotting on the y-axis, against time on the x-axis. It's not the slope but the value the graph is showing at any point in time.
- Acceleration: This represents how quickly the speed is changing over time. If the speed-time graph is linear, then the acceleration is constant, and it’s equal to the slope of the graph.
- Direction: This isn’t quantified on a speed-time graph. Instead, direction might be inferred from a velocity-time graph because velocity is a vector that includes both a magnitude (speed) and a direction.
- Velocity: Similar to speed, velocity is the combination of speed and direction. On a speed-time graph, only the magnitude of the velocity (the speed) is shown. Velocity also changes when acceleration is present, but velocity itself is not represented by the slope of a speed-time graph.
So, the slope of a speed-time graph shows how quickly the object is accelerating or decelerating, which makes 'acceleration' the right choice.
