White water rafting is a popular summer activity.
1. The large rapids in a river usually occur in its narrowest sections. Compare the speed of the water in a wide section of the river to the speed in a narrow section.
2. In slow moving sections of the river you might decide to paddle to propel the raft forward. When you stop paddling the raft will quickly slow down to match the speed of the water. Why?
3. If there is a strong wind blowing up the canyon in which you are rafting your boat may actually stop moving forward. In this case there are four forces acting on the raft, which perfectly balance to keep the boat stationary. What are the four forces?
As you drive down the road in your car, it experiences many forces from the air around it. In answering the following questions assume that your car experiences no internal frictional forces to slow it down.
4. If you are driving very slowly so that the flow of air around your car is laminar your car will still slow down if you coast along a flat horizontal section of road. Why?
5. If you are coasting down a hill your car will eventually settle in at a constant velocity. How does the drag force compare to the car's weight?
6. If you speed up so that the airflow around your car is no longer laminar, how does the pressure at the front of your car compare to the pressure at the back?
7. If you are driving fast enough that the airflow around you car is not laminar, your car will tend to get worse gas mileage if you drive faster than if you drive slower. Why?
8. Again assuming that the airflow around you car is not laminar, your car will tend to get worse gas mileage if you have a large pile of luggage strapped to the top than if there is nothing on you luggage rack. Why?