# physic

posted by
**ray**
.

Average Speed

1. In the 2008 Summer Olympics, Usain Bolt won the 100-m race in 9.69 s. What was his average speed?

2. Light from the sun reaches Earth in 8.3 min. The speed of light is 3.0108 m/s. How far is Earth from the sun?

3. In Major League Baseball, the distance between the pitcher’s mound and home plate is 18.5 m. On September 24, 2010, Aroldis Champman threw a 105-mph fastball. How much time (in s) does the take to get to homeplate?

4. A high school athlete runs 100 m in 12.2 s. What is the athlete’s average speed?

5. Suppose a car travels at a constant speed of 25 mph. How far would it move in (a) 1 hour (b) 1 minute (c) 1 second?

6. To establish the world record for the fastest jet-engined car, the car must travel a distance of 604 m in one direction then travel the same distance in the opposite direction. The first run took 2.12 s and the second run took 2.15 s. (a) What was the average speed for the first run? (b) What was the average speed for the second run?

7. You are driving down a street at 35 mph. Suddenly a child runs into the street in front of you. It takes you 0.75 s to react and slam on the brakes. How many meters do you travel before you begin to slow down?

8. If you drive at 55 mph, how long will it take you to travel from Norfolk to Nags Head N.C., 81.6 miles?

9. If a migrating bird can average 25 mph, how far can this bird travel in 3 weeks? Assume that the bird flies 12 hours per day.

10. A football player runs with an average speed of 9.52 m/s. How much time does it take him to cover 40 yards?

11. If a plane can travel at a speed of 270 mph, how much time will it take to go 852 miles?

12. On the interstate, you pass the 5-mile marker at 9:00 am. At 9:30 am, you pass the 32-mile marker. What is your average speed?

13. In a particle accelerator, an electron can travel at 90% of the speed of light. How far can an electron travel in the blink of eye, 0.9 s?

14. You walk four and a half times around a circular track in 1 hour. The radius of the track is 200 meters. What was your average speed (in m/s)?