“On her return trip, the Proud Mary, going downriver at 11.4 m/s, is backed by a 4.0 m/s current what is her velocity relative to the fisherman on shore?” I don’t just want the answer I want to understand how to do it pls help !

Which types of electromagnetic waves have higher frequencies than the waves that make up ultraviolet light? check all that apply. radio waves infrared light microwaves gamma rays visible light x-rays

Electric field of the earth. the earth has a net electric charge that causes a field at points near its surface equal to 150 n> c and directed in toward the center of the earth. (a) what magnitude and sign of charge would a 60-kg human have to acquire to overcome his or her weight by the force exerted by the earth’s electric field? (b) what would be the force of repulsion between two people each with the charge calculated in part (a) and separated by a distance of 100 m? is use of the earth’s electric field a feasible means of flight? why or why not?

A60-gram sample of radioactive isotope is measured after two half-lives have passed. what pair of percentages describe the sample after two-half lives? a.) 50% unchanged and 50% stable b.) 25% unchanged and 75% stable c.) 12.5% unchanged and 87.5% stable d.) 75% unchanged and 25% stable