If the resistance force is 40 newtons and the effort force is 20 newtons, what is the mechanical advantage?

2 is the mechanical advantage of the machine.

Explanation:

Mechanical advantage of a machine is defined as ratio of force exerted by the machine to the force exerted on the machine.

Resistance force, = 40 N

Effort force, = 20 N

2 is the mechanical advantage of the machine.

t = 1/400 h   ⇔ 0.0025 h ⇔ 9s ⇔ 0.15 m

any of the answers are correct.

3. dark matter

empty space could also be a simple vacuum