Finding time from average speed

In summary, the golfer rides a golf cart at an average speed of 3.1 m/s for 28 seconds and then walks at an average speed of 1.3 m/s for an unknown amount of time. The total distance traveled during the trip is 86.8 meters and the average speed for the entire trip is 1.8 m/s. Using the formula Vave = distance/time, the equation 1.8=(86.8+d)/(28+t) can be formed, where d is the distance walked during the second interval and t is the time taken for the second interval. By substituting the value for d, which is equal to 1.3t, the equation can be solved for t
  • #1
a lone fishy
20
1

Homework Statement



A golfer rides in a golf cart at an average speed of 3.1 m/s for 28s. She then gets out of the cart and starts walking at an average speed of 1.3 m/s. For how long must she walk if her average speed for the entire trip, riding and walking, is 1.8 m/s ?

Homework Equations


[/B]
Vave = distance/time

The Attempt at a Solution


[/B]
This question seems simple considering there's only formula at play. I tried splitting up into 2 parts. The first part, the person walks at an average speed of 3.1 m/s for 28s. Distance can be calculated as 86.8 m

After this I got lost. I know there's a second part where she walks at an average speed of 1.3 m/s. However nothing else is known. And we know her entire average speed is 1.8 m/s

Any ideas?
 
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  • #2
Let ##t## be the time she walks.
You can compute the total time of the trip and the total distance of the trip in function of ##t##.
As you also know the average speed for the entire trip, this will give you an equation in ##t##.
 
  • #3
I didn't quite understand your second line.
Right now I have 1.8=86.8 + d / 28 + t where 1.8 is the average speed of the whole trip, d is the unknown distance from the second interval, and t is the unknown time from the second interval.

Im not sure if I am on the right track nor where to proceed from here

EDIT
where does the 1.3 m/s speed in the second interval come into play?
 
  • #4
a lone fishy said:
I didn't quite understand your second line.
Right now I have 1.8=86.8 + d / 28 + t where 1.8 is the average speed of the whole trip, d is the unknown distance from the second interval, and t is the unknown time from the second interval.

Im not sure if I am on the right track nor where to proceed from here
I assume you meant ##1.8=(86.8 + d) /( 28 + t)##.

You know that she walked at 1.3 m/s, so that should allow you to express ##d## in terms of ##t##.
 
  • #5
Minor correction: she walks at 1.3 m/s
 
  • #6
jbriggs444 said:
Minor correction: she walks at 1.3 m/s
Thanks, I corrected the typo.
 
  • #7
a lone fishy said:
EDIT
where does the 1.3 m/s speed in the second interval come into play?
That's the correct question. You haven't used the 1.3 m/s speed so far.
What relation is there between 1.3 m/s, d and t?
 
  • #8
Ah I think i got it now.

Right now we have the following: 1.8=(86.8+d)/(28+t).

If we find that d then we can have an equation solvable for t.

In interval two we have 1.3 = distance / t
and this equals to: distance = 1.3t

Then we can plug in that value as the d and solve for t :D
 
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Related to Finding time from average speed

1. What is the formula for finding time from average speed?

The formula for finding time from average speed is time = distance / average speed. This means that you divide the distance traveled by the average speed to get the time taken to cover that distance.

2. How do you calculate average speed?

To calculate average speed, you divide the total distance traveled by the total time taken. This formula can be written as average speed = distance / time. Make sure that the distance is measured in the same units as the time (e.g. meters and seconds).

3. Can average speed and time be negative?

No, average speed and time cannot be negative. Average speed is a measure of how fast an object is moving in a certain direction, and time is a measure of duration. Both of these values can only be positive or zero.

4. Why is it important to calculate time from average speed?

Calculating time from average speed is important in many scientific and real-world applications. It can help us determine how long it will take to reach a destination, how much time it will take to complete a task, and can also be used to analyze and compare the efficiency of different modes of transportation.

5. Can you use the formula for finding time from average speed for any type of motion?

Yes, the formula for finding time from average speed can be used for any type of motion as long as the average speed remains constant throughout the entire journey. If the average speed changes, you would need to use a different formula to calculate the time taken for each segment of the motion.

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