You will need
  • Calculator, pen
Own speed is the speed of the boat or another vehicle in still water. Her mark - V own.
The water in the river is moving. So it has its speed, called the speedu of the flow (V tech.)
The speed of boats on the river mark - V via tech., and the speed upstream is V PR. tech.
Now remember the formulas required to solve problems on the motion:
V PR. tech.= V own. - V tech.
V on tech.= V own. + V tech.
So, based on these formulas, we can draw the following conclusions.
If the boat moves against the river's current, V own. = V PR. tech. + V tech.
If the boat moves with the current, then V own. = V on tech. - V tech.
Solve some of the problems on the motion on the river.
Task 1. The speed of the boat against the river's current 12.1 km/h. Find your own speed boats, knowing that the speed of river is 2 km/h.
Solution: 12,1 + 2 = 14, 1 (km/h) - private speed boat.
Task 2. The speed of boats on the river 16.3 km/h, the speed of the river is 1.9 km/HR How many metres would have passed this boat for 1 min., if it was placed in still water?
The decision of 16.3 and 1.9 = 14.4 V (km/h) - private speed boat. Translate km/h to m/min: 14.4 V / 0,06 = 240 (m/min). So in 1 minute the boat was 240 m.
Task 3. Two boats went at the same time towards each other from two points. The first boat moved up the river, and the second - against the current. They met in three hours. During this time the first boat was 42 km, and the second is 39 km away and Find your own speed of each boat if it is known that the speed of river is 2 km/h.
Solution: 1) 42 / 3 = 14 (km/h) - speed of traffic on the river the first boat.
2) 39 / 3 = 13 (km/h) - the speed of the movement against the current of the river a second boat.
3) 14 - 2 = 12 (km/h) - speed of the first boat.
4) 13 + 2 = 15 (km/h) - speed of a second boat.