VIEWS: 204 PAGES: 2 POSTED ON: 3/25/2011
Kinematic Equations Review Average Speed and Velocity 1. Three-and-a-half seconds after seeing lightning you hear the thunder. If the speed of sound in air at that moment is 340 m/s, how far away was the lightning bolt? 2. A finch rides on the back of a tortoise, which walks at a steady pace of 0.06 m/s. After 2 minutes the finch takes flight in the same direction at a speed of 12 m/s for 2 minutes. What was the average speed of the finch over this 4-minute time interval? 3. A car travels in a straight-line path at 20 m/s for 10.0 minutes then at 30.0 m/s for another 10.0 minutes. Is the car's average velocity … a) 25 m/s; b) >25 m/s; c) <25 m/s? 4. A car travels in a straight-line path at 20 m/s for 10.0 miles then at 30.0 m/s for another 10.0 miles. Is the car's average velocity … a) 25 m/s; b) >25 m/s; c) <25 m/s? Acceleration 5. At the starting gun, a runner accelerates at 1.9 m/s/s for 2.2 s. The runner's acceleration is zero for the rest of the race. What is the speed of the runner a) at t = 2.0 s, and b) at the end of the race? 6. An object has an acceleration of +6.24 m/s/s for 0.300 s. At the end of this time the object's velocity is +9.31 m/s. What was the object's original velocity? 7. Running with an initial velocity of +11 m/s, a horse has an average acceleration of -1.81 m/s/s. How long does it take for the horse to decrease its velocity to +6.5 m/s? Motion with Constant Acceleration 8. A cheetah accelerates from rest to 25 m/s in 6.2 s. How far does it travel in 6.2 s? How about in half that time? 9. Starting from rest, a boat increases its speed to 4.30 m/s. A) What is its average speed? B) If it takes 5 s to reach this speed, how far does it travel? Applications of the Equations of Motion 10. A child starting at rest slides downhill on a toboggan with an acceleration of 1.5 m/s/s. How far does she travel in a) 1s, b) 2 s, and c) 3 s? 11. A boat is cruising at a constant speed of 2.2 m/s when it is shifted into neutral. After crossing 10.0 m the engine is engaged again, and the boat resumes cruising at the reduced speed of 1.6 m/s. How long did it take for the boat to coast the 10.0 m? 12. The San Diego chicken rounds 3rd base with a speed of 6.0 m/s and slides into home plate. If the chicken slides for 1.2 s before resting upon home plate, what was his acceleration? How far did he slide? Freely Falling Objects 13. At his best, Michael Jordan's vertical leap was said to be 48 inches. What is his take-off speed? 14. A hot air balloon is descending at a rate of 2.0 m/s when a passenger drops his camera. If the camera is 45 m above the ground when it is dropped, a) how long does it take to reach the ground, and b) what is its velocity as it strikes the ground? 15. You foolishly shoot an arrow straight into the air. Two seconds later it is 30.0 m above you. What was its initial velocity? 16. While sitting in an apple tree 10 m above the ground, you drop an apple. When the apple has fallen 2.5 m you throw another apple downward. What velocity must the second apple have in order to hit the ground simultaneously with the first? Answers 1) 1190 m; 2) 6.0 m/s; 3) A; 4) C; 5a) 3.8 m/s; 5b) 4.18 m/s; 6) 7.44 m/s; 7) 2.5 s; 8a) 78 m; 8b) 19 m; 9a) 2.15 m/s; 9b) 10.8 m/s; 10a) 0.75 m; 10b) 4x that; 10c) 9x that; 11) 5.3 s; 12a) 5.0 m/s/s toward 3rd base; 12b) 3.6 m; 13) 4.9 m/s; 14a) 29.8 m/s; 14b) 2.83 s; 15) 24.8 m/s; 16) 10.5 m/s