Answer:
a. positive
b. negative
c. zero
d. negative
Explanation:
You want a description of the sign of the slope of a graph of ...
- amount of water in a filling bathtub
- temperature of a cooling drink
- number of lights in a string
- power in a battery being used
Slope
The slope of a graph is the "rise" divided by the "run." Generally, we choose the direction of "run" to be to the right, so the "rise" will be positive when the graph shows an increasing value, and it will be negative when the graph shows a decreasing value. When the rise is zero (the value is neither increasing nor decreasing), the slope is zero.
Water
A graph of the volume of water in a filling tub will show it starts at some low value and increases over time. Generally such a graph will have volume on the vertical axis, and time on the horizontal axis. Since the volume is increasing, the slope is positive.
Temperature
As a hot drink cools, its temperature decreases. The graph of temperature will generally be drawn with temperature on the vertical axis, and time on the horizontal axis. Since the temperature is decreasing, the slope will be negative.
Lights
We presume there is no process going on that is changing the number of light bulbs in the string of lights, so the value is constant. It is neither increasing nor decreasing, so the slope of its graph will be zero.
Power
If we presume your cell phone is not connected to a charger while it is streaming video for you, then we can assume the power in the battery is decreasing. The slope of the graph of battery power will be negative.
(If the phone is connected to a charger, the slope may be zero or positive, depending on the power output of the charger. One of my phone chargers is "low power," so the battery power does not increase unless the phone is turned off (not playing video).)