Calc force needed given objects mass & required acceleration

[Amelina Yoo]

Homework Statement

What is the force needed to accelerate a 2.0kg ball at 3.0ms^-2

a) In a frictionless horizontal surface, near the surface of the Earth
b) Vertically upward, near surface of the Earth

Homework Equations

f=ma
w=mg

The Attempt at a Solution

For a) F=2(3) = 6N
By inputing the variables into the formula, I got to an answer. but, I do not know how a) differs from b), as in what route to do for b...

Thank you for any help. :-)

 

[haruspex]

At Earth's surface, what force has to be applied to the object just to keep it where it is?