Final answer:
A minus sign indicates a value less than zero, a plus sign means greater than zero, and no sign typically implies a positive value. In physics, these signs are used to denote the direction of motion, with negative acceleration indicating deceleration. The temperature is a scalar quantity, where the negative sign simply denotes a value below zero.
Step-by-step explanation:
Before a weather phenomenon or in the context of physics, a minus sign (-), no sign, or a plus sign (+) may indicate different things. A minus sign before a number signifies that it is less than zero, whereas a plus sign indicates a number greater than zero. By convention, no sign before a number typically implies a positive value. These signs are especially important when describing motion in physics. For example, an object moving downward typically is assigned a negative sign due to the conventional direction of the coordinate system in which up is positive and down is negative.
Regarding one-dimensional motion, plus and minus signs are used to indicate direction. If the sign of an acceleration is the same as the sign of the current velocity, the object is speeding up. If the acceleration sign is opposite to that of the velocity, the object is slowing down. For instance, a positive acceleration would reduce the magnitude of a negative velocity, but if both the velocity and acceleration are negative, the object's speed increases.
A practical example would be an airplane landing on a runway traveling east. If east is considered positive, then as the airplane is decelerating, or slowing down, it would be experiencing negative acceleration. The direction of the acceleration is westward, which is the opposite to the airplane's velocity. It's important to note that this directionality is indicated by the sign placed before the values of displacement, velocity, or acceleration.
Temperature, as predicted in a weather forecast, such as -5°C, is a scalar quantity. The negative sign here simply indicates that the temperature is below zero and does not imply direction, which is required for a vector.