Question

A small boat moving at 15 km/h crosses a 350 m wide river. The water runs at 6 m/s towards the left. Calculate: 5.1 The time it takes the boat to cross the river

Answer 1

To calculate the time it takes the boat to cross the river, we first need to calculate the velocity of the boat relative to the water.

The boat is moving at 15 km/h, which is equal to 15,000 m/3600 s = 4.17 m/s.

The river is flowing at 6 m/s towards the left.

Therefore, the velocity of the boat relative to the water is the vector sum of these velocities, which is the square root of (6^2 + 4.17^2) = 7.17 m/s.

Now that we have the velocity of the boat relative to the water, we can calculate the time it takes the boat to cross the 350 m wide river:

Time = Distance / Velocity
Time = 350 m / 7.17 m/s
Time ≈ 48.82 seconds

So, it will take the boat approximately 48.82 seconds to cross the river.