Indeterminate?

[Randyyy]

Hey Mathhelp, the task goes as following: " Assume your average velocity to point A is 10 km/h. What speed do you have to drive back with to have an average velocity of 20 km/h?

My attempt:

The displacement call it d is the same for both trips.
d=V₁ t₁ and d=V₂t₂, V average = d/t, so 2d/t₁+t₂=V and doing the algebra i eventually stumble up at 200/0 which of course is indeterminate, but what does it mean? Does it mean I calculated it incorrectly or is it simply not possible? feels like somewhere along the line it is wrong because you could always compensate by driving faster or slower.

 

[LCKurtz]

It can't be done. To do the trip at an average of [MATH]20[/MATH] you need [MATH]\frac{2d}{20}=\frac d {10}[/MATH] hours. You have used all that time outbound. No time left to return.

 

[Dr.Peterson]

Hey Mathhelp, the task goes as following: " Assume your average velocity to point A is 10 km/h. What speed do you have to drive back with to have an average velocity of 20 km/h?

My attempt:

The displacement call it d is the same for both trips.
d=V₁ t₁ and d=V₂t₂, V average = d/t, so 2d/t₁+t₂=V and doing the algebra i eventually stumble up at 200/0 which of course is indeterminate, but what does it mean? Does it mean I calculated it incorrectly or is it simply not possible? feels like somewhere along the line it is wrong because you could always compensate by driving faster or slower.

200/0 is not indeterminate; it is infinite, in the sense of a limit. In effect, you would have to get back instantaneously (infinite speed) in order to average 20 km/h.