1. A yacht is 20 m long. Express this length in feet.

2. A convenient time unit for short time intervals is the millisecond. Express 0.0452 s in milliseconds.

3. A hypnotist's watch hanging from a chain swings back and forth every 0.8 s. What is the frequency of its oscillation?

4. A passenger jet flies from one airport to another 1,200 miles away in 2.5 h. Find its average speed.

5. A runner in a marathon passes the 5-mile mark at 1 o'clock and the 20-mile mark at 3 o'clock. What is the runner's

6. In Figure 1.13, assume that v1 = 8 m/s and v2 =6 m/s. Use a ruler to estimate the magnitudes of the resultant velocities in (c) and (d).

7. How far does a car going 25 m/s travel in 5 s? How far would a jet going 250 m/s travel in 5 s?

8. Draw an accurate graph showing distance versus time for the car in Problem 13. What is the slope of the graph?

9. A high-performance sports car can go from 0 to 100 mph (44.7 m/s) in 7.9 s. (a) What is the car's average acceleration? (b) The same car can come to a complete stop from 30 m/s

in 3.2 s. What is its average acceleration?

10. A child attaches a rubber ball to a string and whirls it around in a circle overhead. If the string is 0.5 m long and the ball's speed is 10 m/s, what is the ball's centripetal acceleration?

11. A runner is going 10 m/s around a curved section of track that has a radius of 35 m. What is the runner's acceleration?

12. A rocket accelerates from rest at a rate of 60 m/s2. (a) What is its speed after it accelerates for 40 s? (b) How long does it take for the rocket to reach a speed

of 7,500 m/s?

13. (a) Draw an accurate graph of the speed versus time for the train in Problem 24. (b) Draw an accurate graph of the distance versus time for the train in Problem 24.

14. A skydiver jumps out of a helicopter and falls freely for 3 s before opening the parachute. (a) What is the skydiver's downward velocity when the parachute opens? (b) How far below the helicopter is the skydiver when the parachute opens?

15. The roller coaster in Figure 1.39 starts at the top of a straight track that is inclined 30 with the horizontal. This causes it to accelerate at a rate of 4.9 m/s2 (1/2 g). (a) What is the roller coaster's speed after 3 s?

(b) How far does it travel during that time?