A student can row a boat 6km/h in still waters, she is on one bank of a 6 km wide river that has current of 3km/h. Assuming she is allowed to land anywhere on the shore: (i) What is the smallest amount of time she needs to get to the opposite bank? (ii) What is the student’s speed as viewed by the observer on the bank?

(Figure 1)A swimmer wants to cross a river, from point A to point B, as shown in the figure. The distance d₁ (from A to C) is 200 m, the distance d₂ (from C to B) is 150 m, and the speed vr of the current in the river is 5 km/hour. Suppose that the swimmer's velocity relative to the water makes an angle of 0 = 45 degrees with the line from A to C, as indicated in the figure. To swim directly from A to B, what speed us, relative to the water, should the swimmer have? Express the swimmer's speed numerically, to three significant figures, in kilometers per hour.

A boat crosses a river of width 159 m in which the current has a uniform speed of 1.63 m/s. The pilot maintains a bearing (i.e., the direction in which the boat points) per- pendicular to the river and a throttle setting to give a constant speed of 1.45 m/s relative to the water. What is the magnitude of the speed of the boat relative to a stationary shore observer? Answer in units of m/s. Answer in units of m/s. 1. 3.2032 2. 1.91816 3. 2.06662 4. 3.68893 5. 2.91302 6. 3.61411 7. 2.1816 8. 1.60269 9. 2.0297 10. 1.19289

A medieval city has the shape of a square and is protected by walls with length 500 m and height 15 m. You are the commander of an attacking army and the closest you can get to the wall is 100 m. Your plan is to set fire to the city by catapulting heated rocks over the wall (with an initial speed of ( 80m/s). At what range of angles should you tell your men to set the catapult? (Assume the path of the rocks is perpendicular to the wall.)

Airplane flight recorders must be able to survive catastrophic crashes. Therefore, they are typically encased in crash-resistant steel or titanium boxes that are subjected to rigorous testing. One of the tests is an impact shock test, in which the box must survive being thrown at high speeds against a barrier. A 43-kg box is thrown at a speed of 340 m/s and is brought to a halt in a collision that lasts for a time of 6.6 ms. What is the magnitude of the average net force that acts on the box during the collision?

A boat heads directly accross a river 220 m wide. it takes it 570 seconds to cross, but it ends up 100 m downstream. what its peed relative to the water? that is how fast is the boat?