What ion movement changes the membrane potential in a contractile cell from negative to positive during the rapid depolarization phase?

The influx of calcium ions.

Explanation:

The influx of calcium ions at a certain point produces phase of the action potential also called depolarization which results in the ion movement changes the membrane potential from negative to positive inside the cell.

In action potential, calcium ions may control gene transcription, cell excitability, and neurotransmitter release. In chemical synapses, the influx of calcium ions leads to vesicles filled with neurotransmitters move to the surface of the cell, and into the synaptic cleft release their contents.

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.

answer; i believe the correct answer to the above question is ( friction)