Why does passive transport not require the cell to use energy to move molecules across the membrane? The molecules are moving from high concentration to low concentration.

The molecules use water to move across the plasma membrane.

The molecules use protein pumps to move molecules across the membrane.

The molecules are moving against the concentration gradient.

the answer is; comparing the frequency of collisions with and without the device

this makes the anti-collision system an independent variable and the collisions a dependent variable. if there are fewer collisions with an anti-collision system that without, then it can be stated that the system is a success. essentially, collisions under an anti-collision system are compared with the frequency of collisions by cars with the human drivers.