# I Am In class 9Please Tell The Concept Behind The Pulley Problems And River Boat Problems

Rohit Girdhar
25 Points
9 years ago

Hi,

I am very glad that you are concerned for this topis this early. Theses are very easy topics when studied by understanding the concept. I will suggest you to buy HC Verma book for Physics for class 11th anlthough its for 11th, but i am sure that u will be able to understand it due ti its simple and easy to understand language.

River Boat Problem

It is a question in which one is given speed of the river generally in horizontal direction. We represent by either ''u'' or ''VR'' the we are given velocity of swimmer in still water assuming that the water is not moving in the river body. There r 2 cases of shortst distance and time. for shortset time the swimmer should swip perpendicular to the river flow so that it gets carrired along with the flow and reach the opposite side as quickly as possible. IIt''s formulae is d/vsr where d is the total widtg of the river and vsr is the velocity of swimmer in stil water. For shortest distance he should swim at an angle left towards the vertical if the river is towards right ( Flowing ). its formulae is d/vs where we can represent vs and underoot of vsrsquare - vrsquare. I hope this helps.

Rohit

mahendra shah
19 Points
9 years ago

concept behind pulleys is just balancing forces and calculating acceleration related with unbalanced forces.

post an example for further clarification..