1. A woman standing before a cliff claps her hands, and 2.8 s later she hears the echo. How far away is the cliff? The speed of sound in air at ordinary temperatures is 343 m/s. 2. The starter of a race stands at one end of a line of runners. What is the difference in time between the arrival of the sound of his pistol at the nearest runner and at the most dis- tant runner 10 m farther away? (In a sprint, 0.01 s can mean the difference between winning and coming in second.) 3. In 1977 Steve Weldon ate 91 m of spaghetti in 29 s. At the same speed, how long would it take Mr. Weldon to eat 5 m of spaghetti? 4. A snake is slithering toward you at 1.5 m/s. If you start walk- ing when it is 5 m away, how fast must you go so that the snake will not overtake you when you have gone 100 m? 5. A woman jogs for 2 km at 8 km/h and then walks for 2 km at 6 km/h. What is her average speed for the entire trip? 2.2 Vectors 6. Three forces, each of 10 lb, act on the same object. What is the maximum total force they can exert on the object? The minimum total force? 7. Is it correct to say that scalar quantities are abstract, idealized quantities with no precise counterparts in the physical world, whereas vector quantities properly repre- sent reality because they take directions into account? 8. A man is rowing at 8 km/h in a river 1.5 km wide in which the current is 5 km/h. (a) In what direction should he head in order to get across the river in the shortest possible time? (b) How much time will he take if he goes in this direction? (c) How far downstream will the boat have gone when it reaches the opposite side? 9. A woman walks 70 m to an elevator and then rises upward 40 m. What is her displacement from her starting point? 10. Two tugboats are towing a ship. Each exerts a horizontal force of 5 tons and the angle between their towropes is 90". What net force is exerted on the ship