The _______ speed of a car at any instant can be determined by its speedometer.
instantaneous
Understanding How a Car Speedometer Measures Speed
The question asks about the specific type of speed that a car's speedometer measures at any given moment. Let's break down the different concepts related to speed to understand what a speedometer indicates.
What is Speed?
Speed is a measure of how fast an object is moving. It tells us the distance covered per unit of time. There are different ways to think about speed:
- Average Speed: This is the total distance traveled divided by the total time taken for the entire journey. It doesn't tell you how fast you were going at any specific point during the trip.
- Instantaneous Speed: This is the speed of an object at a particular moment in time. If your speed is changing, the instantaneous speed is the speed shown on the speedometer right at that instant.
How a Speedometer Works and What It Measures
A car's speedometer is designed to show you how fast your car is moving right now. It responds very quickly to changes in the car's speed. For example, if you accelerate, the needle or digital display on the speedometer immediately shows an increase in speed. If you brake, it shows a decrease. This immediate indication of speed at any given moment is the definition of instantaneous speed.
Analyzing the Options for Speed Measurement
Let's look at the given options:
- Spontaneous: This word means happening suddenly or without external cause. It doesn't relate to a type of speed measurement.
- Instantaneous: This refers to something happening or existing at a particular instant in time. As discussed, a speedometer measures the speed at that specific moment.
- Maximum: This is the highest speed achieved during a period of travel. While the speedometer will show the maximum speed when you reach it, its primary function is to display the speed *at any instant*, not just the maximum.
- Natural: This refers to something existing in or derived from nature. It has no relevance to the measurement of a car's speed.
Based on the analysis, the speed indicated by a speedometer at any instant is the instantaneous speed.
| Type of Speed | Description | Measured by Speedometer? |
|---|---|---|
| Average Speed | Total distance / Total time over a journey | No (calculated over time) |
| Instantaneous Speed | Speed at a specific moment in time | Yes |
| Maximum Speed | Highest speed reached during a journey | Only at the moment it is reached |
Therefore, the correct word to complete the sentence is 'instantaneous'.
Revision Table: Key Speed Concepts
| Term | Meaning | Relevance to Speedometer |
|---|---|---|
| Instantaneous Speed | Speed at a single point in time | What a speedometer measures constantly |
| Average Speed | Overall speed over a distance/time | Not measured directly by speedometer |
Additional Information on Speed Measurement
Early speedometers used mechanical means, connecting a rotating cable from the car's transmission to a dial. Modern speedometers are typically electronic, using sensors on the transmission or wheel hubs to measure rotation speed and calculate the instantaneous speed displayed to the driver. While speedometers are generally accurate, there can be small variations. They always display the speed at the precise moment the reading is taken.
Important Questions from Motion
An object is covering distance in direct proportion to the square of time elapsed. What conclusion can be drawn about the motion of the object?
If the distance time graph of the motion of an object is a straight line but not parallel to the time axis, then it may be concluded that the object is moving with a:
Which of the following changes when a body performs uniform circular motion?
Vehicles have treaded tires so that it_______.
The distance time graph for an object, moving with a constant speed will be a
