How would you answer this?

Question

If the forces acting upon an object are balanced, then the object...

a) must not be moving

b) must be moving at a constant velocity

c) must be accelerating

d) none of these

Answer 1

If the forces are balanced that means the sum of the forces is zero. Since F = ma, or in this case ∑F = ma, then if ∑F = 0 then acceleration = 0 (assuming the object has mass). An acceleration of zero could mean the object is still or that it is moving at constant velocity. So I would say the answer is D.