What is main difference between a lake ecosystem and a pond ecosystem?

a. a lake ecosystem has salt water a pond ecosystem does not

b. a pond ecosystem has salt water a lake ecosystem does not

c. a pond ecosystem covers a much larger area than a lake ecosystem

d. a lake ecosystem covers a much larger area than a pond ecosystem

We put a force of 50n on an object and the acceleration is 100 m/s². what is the mass of the object?

Consider a uniformly charged ring in the xy plane, centered at the origin. the ring has radius a and positive charge qdistributed evenly along its circumference. a)what is the direction of the electric field at any point on the z axis? . b)what is the magnitude of the electric field along the positive z axis? use k in your answer, where k=14πϵ0. d)the ball will oscillate along the z axis between z=d and z=−d in simple harmonic motion. what will be the angular frequency ω of these oscillations? use the approximation d≪a to simplify your calculation; that is, assume that d2+a2≈a2. express your answer in terms of given charges, dimensions, and constants

Why does lightning travel from clouds to the ground?