June 2006 M1 (7iii)

Hey.
I don`t quite understand why i cannot use the acceleration i found in part i to do part iii.
What has caused acceleration to change?
Thanks

Going up the plane, both friction and the component of the weight were acting down the plane. Now that you're coming down, the component of the weight is still acting down the plane but the friction is acting up the plane, so the acceleration is different.