To solve this physics question about a boat traveling downstream and upstream, we need to use the concept of relative velocity. The boat's speed and the river's speed are used to calculate the time required for different scenarios.
In this question, we are dealing with the concept of relative velocity. To solve part (a), we can use the formula: time = distance / relative velocity. The relative velocity is the difference between the boat's speed and the river's speed. Therefore, the time required to row 1.5 km downstream is 1.5 km / (8.0 km/h + 3.0 km/h). Solving for time gives us the answer for part (a). Similarly, for part (b), we can use the same formula, but the relative velocity is now the difference between the boat's speed and the river's speed in the opposite direction. Finally, for part (c), the boat must be aimed directly perpendicular to the river current, so that its motion and the river's motion are at right angles. This will allow the boat to row straight across the river.
Upstream: A boat is said to be moving upstream when it is moving against the stream. Here, the boat's net speed is referred to as the upstream speed. Downstream: The boat is said to be downstream if it is moving in the stream's direction.