Answer: The gravitational acceleration on planet X is 5 N/kg
On Earth (with the gravitational accelartion g_E) the mass of 2kg will correspond to

On planet X we are told the same measure is only 10N. Since there is a proportional relationship between g and F, we can calculate g_X:

I believe Action potential is the brief wave of positive charge that sweeps down the axon. Axon is part of the neuron that conducts impulses from the dendrites towards the cell body along the neuron. The action potential is brief since the sodium channels can only stay open for a very brief amount of time. As it travels along the neuron there is a change in polarity across the membrane of the axon .
Vt = Vboat - Vriver
Vt = 18 - 2.5 = 15.5 m/s
If the boat's direction is the same as the water, you sum the velocities of the river and the boat .