You and a friend plan to throw one end of a hose over a tall fence to siphon water from your side to the other side. Your friend says it doesn't matter how high the fence is, it will always work as long as your end of the hose is higher than the other side. However, you remind him that isn't actually true. What is the potential problem and about how high can the fence be (in meters) before it becomes an issue?

1. A new town is being developed in a rural area of Costa Rica. Planners are projecting a population of about 2,000 people and a baseload electric energy demand for the town of 10MWe over the first 20 years. A nearby river flows from the rainforest region with a mean annual flow of 100m³/s. Over a 20 km distance upstream of the town site, the river has a change in elevation of 1,000 m. Seasonal variations in the river flow could be as large as a factor of ten above or below the mean flow. Is a hydro project using turbines with 80% efficiency feasible to meet the town's future energy needs? Discuss (2-3 sentences each) at least two associated impacts that planners also need to consider in the hydro project design.

1. You are setting up for a pool party that has a 2.5 m high slide that launches swimmers into the pool. To make it more exciting, you decide to string a steamer across the pool so that the swimmers just clear it at their maximum height after leaving the slide. The end of the slide is 0.75 m above the ground and is directed 20° above the horizontal. By watching people use the slide, you know the horizontal distance to place the streamer, so you only need to determine the maximum height. You are also curious how fast the swimmers are going when they enter the pool. In your estimates, you can assume that the swimmer starts at rest at the top of the slide and ignore friction on the slide and air resistance. 2.5 m 0.75 m streamer If the angle of the slide were different (say 15°) would either the maximum height or the speed when entering the water be different? Note: Use conservation of energy to answer these questions.