Solving the Car's Speed: Radar Velocity and Reflection

In summary, the conversation discusses a scenario where a car is driving west and a patrol officer is driving east at a certain velocity. The officer's radar gun indicates that the car is speeding, and the conversation goes on to calculate the velocity of the car using the radar gun's frequency and a given equation. The final answer is 85.2m/s, and the conversation also mentions finding and correcting a previous error in the equation.
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qestion
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Homework Statement


A car is driving west and a patrol officer is driving east at 23.50 m/s. The officer's radar gun indicates that the car is speeding. If the radar gun sends out a frequency of 24.15GHz and receives a reflected signal of 24.20GHz, what is the velocity of the car? (Assume radar velocity is 2.750x10^4 m/s)

Homework Equations


fo=fs((V±Vo)/(V±Vs))

The Attempt at a Solution


2.415e9Hz=2.42e9Hz((331m/s+23.50m/s+2.75e4m/s)/(331m/s-Vs+2.75e4m/s))

Vs=81.2m/s

What is wrong with this, and what exactly should I be doing with the radar velocity?

Never mind, I found my error.
 
Last edited:
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  • #2
The equation should have been2.42e9Hz=2.415e9Hz((331m/s-23.5m/s+2.75e4m/s)/(331m/s-Vs+2.75e4m/s))Vs=85.2m/s
 

1. How does radar velocity help determine a car's speed?

Radar velocity is a method of measuring the speed of an object by using radio waves. These waves are transmitted from a radar gun and bounce off the moving object, before being received back by the radar gun. The change in frequency of the waves (known as the Doppler effect) can then be used to calculate the speed of the object.

2. What factors can affect the accuracy of radar velocity in determining a car's speed?

There are several factors that can affect the accuracy of radar velocity, such as weather conditions (rain or fog can interfere with the radar waves), the angle and distance of the radar gun from the moving car, and the speed of the car itself. Additionally, radar velocity can be affected by other objects in the surrounding environment, including large buildings, trees, or other vehicles.

3. Is radar velocity the only method used to measure a car's speed?

No, radar velocity is just one of several methods used to measure a car's speed. Other methods include laser technology, visual estimation by a trained police officer, and speed cameras. Each method has its own advantages and limitations, and may be used in different situations or by different agencies.

4. Can radar velocity be used to track multiple cars at once?

Yes, radar velocity can be used to track multiple cars at once. This is possible because the radar waves can bounce off multiple objects and the radar gun can detect and measure the speed of each one. However, the accuracy of the readings may be affected if the objects are too close together or if there is interference from other objects or sources.

5. How can radar velocity be used to enforce speed limits on roads?

Radar velocity is commonly used by law enforcement to enforce speed limits on roads. Police officers may use handheld radar guns to determine the speed of individual cars, or they may set up radar speed traps along a stretch of road. The radar readings are then used as evidence to issue speeding tickets or to support other traffic violations.

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