Explain why is it difficult for a fire man to hold a hose, which ejects large amount of water at a high velocity

A sphere of charge + Q is fixed in position. A smaller sphere of charge + q is placed near the larger sphere and released from rest. The small sphere will move away from the large sphere with decreasing velocity an inreasing acceleration, decreasing velocity and increasing acceleration, decreasing velocity and constant acceleration, increasing velocity and increasing acceleration explain, which of the following statements is correct?

Explain why water has high boiling and melting points as compared to H_2S

Create an aquatic food chain in a water body into which effluents flow from a pesticide factory. Diagrammatically represent biomagnification in this food chain Explain why a decline in the predator bird population is expected when its feeds on the tertiary consumer of this food chain.

In case of a fire , before the fireman use the water hoses , they shut off the main electrical supply for the area. Explain why they do this.