Average Speed Calculation: Why 2x266.67 Doesn't Work

[Janiceleong26]

1. Homework Statement

Ok so for part ii) b)

I calculated the average speed as follow,
Average speed= 3792.6/ (2x266.67), where 3792.6m is the total distance, and 266.67s is the time when v=0 , i.e. the time from O to the turning point

But it should be 3792.6/ 400, where 400s is the time when x=0 , i.e. returns to O

I'm confused, why isn't the total time (2x266.67) ? What is there a difference in the time?

 

[PeroK]

Why do you think it takes as long to get back from the turning point as it does to reach it?

 

[BvU]

Yes there is. v is not symmetric as with constant acceleration. Make a sketch.