What Speed Do You Need for the Rest of Your Trip to Average 2 m/s?

[nviander]

Homework Statement

In going to the store, you walk half of the distance at 1 m/s. At this point, you decide that you should pick up the pace. You would like to average 2 m/s for the entire trip. How fast must you move for the remainder of your trip in order to do so? Hint: the answer is not 3 m/s!

Homework Equations

v = 0.5 (v[1] + v[2])

The Attempt at a Solution

v = 0.5 (v[1] + v[2])
2 = 0.5 (1 + v[2])
2 = 0.5 + 0.5v[2])
1.5 = 0.5v[2]
3 = v[2]

 

[Dale]

Suppose the total distance is 100 m. How long do you have to make the whole trip? How much time do you have left?

 

[BvU]

Hello nv, welcome to PF :)
Average v is distance / time. If your distance is 3.6 km you can work out the time you need at 1 m/s.
And the time you allow yoursself, considering the desired average speed.
You can work out how far you got in half the time and you can work out how much time you have left for the remainder of the distance.

Bingo, except that the exercise doesn't say the distance is 3.6 km. Call it d or x or y and repeat the exercise.

[edit]Dale is so fast ! He'll help you out...

 

[nviander]

Suppose the total distance is 100 m. How long do you have to make the whole trip? How much time do you have left?

Oh my goodness. This is actually so simple. Thank you so much for helping me!

 

[HalfLostAndSearching]

To average 2 m/s for the entire trip, you would need to move at a speed of 3 m/s for the remainder of your trip. However, this is not possible as you have already walked half of the distance at a speed of 1 m/s. Therefore, it is not possible to average 2 m/s for the entire trip.