Question

Why will a toy train remain still if you push on the engine with

Answer 1

Explanation:

Because when two equal forces are applied from opposite directions, they "eliminate" each other.

The train would go right if a 3N force was only applied in the right direction, and it would go left if the same force was only applied to the left.

If a 3N force was applied to the right and a 2N force to the left, it would equal a 1N force to the right (3-2=1).

But there it's 3-3=0, so in practice the force is 0N. Therefore the train won't move.