Understanding Average Speed Calculations

In summary, the question involves a motorist traveling at different speeds over a total distance of 90 miles. The average speed is 36 mph, which is calculated by dividing the total distance by the total time taken. This is because the motorist spends half the distance at each speed, resulting in a total time of 2.5 hours. This method is used instead of the formula vaverage = (v1 + v2)/2 because the speed is not constant throughout the entire journey.
  • #1
rcmango
234
0

Homework Statement



theres a motorist that travels 30 miles at 60 mph, and another 60 miles at 30 mph.


Homework Equations





The Attempt at a Solution



The average speed of the motorist is 36 mph
how was this computed?

i know avg speed is distance / chng of time

however 30+ 60 divided by 60 + 30 is not 36.
need help.
 
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  • #2
Please write the full question.
 
  • #3
...nevermind i think it got it,

since he's traveling only half the distance of what speed he's going, then he probably only went about 30 minutes, and then the oppositive of that with the other, which is 2 hrs, then distance of 90 / 2.5 hrs is the avg speed of 36 m/s

thanks anyway.
 
  • #4
good!
just to, may be, boost up your knowledge:
can you tell, why vaverage = (v1 + v[2)/2 is not applicable here? {Note, it would give 45mph}
Also, note that constant speed is provided in either part of the motion.
 

Related to Understanding Average Speed Calculations

1. What is an average speed problem?

An average speed problem is a type of mathematical problem that involves finding the average speed of an object over a certain distance and time. It is commonly used in physics and other sciences to calculate the average rate of change of an object's position over time.

2. How do you solve an average speed problem?

To solve an average speed problem, you need to know the distance an object travels and the time it takes to travel that distance. Then, you can use the formula average speed = distance/time to calculate the average speed.

3. What units are used for average speed?

The most common units used for average speed are meters per second (m/s) and kilometers per hour (km/h). However, other units such as miles per hour (mph) and feet per second (ft/s) may also be used depending on the context.

4. How is average speed different from instantaneous speed?

Average speed is the overall rate of change of an object's position over a certain distance and time, while instantaneous speed is the speed of an object at a specific moment in time. Average speed takes into account the entire journey, while instantaneous speed only considers a specific point.

5. Can average speed be negative?

Yes, average speed can be negative if the object is moving in the opposite direction of the chosen reference point. For example, if an object travels 10 meters north in 5 seconds and then travels 10 meters south in 5 seconds, the average speed would be 0 meters per second (m/s) but it would also have a negative direction (-10 m/s).

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