Falling Bodies and Free-Fall Acceleration

1. Falling Bodies and Free-Fall Acceleration

2. Hammer and Feather

3. How is the acceleration rate of objects on the moon different from the acceleration of objects on Earth?

4. ANSWER • It’s about 1/6 the acceleration of objects on Earth……approx 1.6m/s2

5. WHAT IS FREE-FALL ACCELERATION?

6. Free-Fall Acceleration • A free falling object is an object that is falling under the sole influence of gravity. There are two important motion characteristics that are true of free-falling objects: 1. Free-falling objects do not encounter air resistance. 2. All free-falling objects (on Earth) accelerate downwards at a rate of 9.81 m/s2 (often approximated as 10 m/s2.

7. Who was the first scientist to prove that all objects fall at the same rate in the absence of air resistance?

8. VIDEO

9. Free- Falling Objects If there is NO AIR RESISTANCE, ALL objects, regardless of weight & size, will fall at the same acceleration. The Acceleration due to gravity: (Free-fall acceleration) g= 9.81 m/s2, down

10. How does the velocity of the object change as it falls? • The position of the free-falling object at regular time intervals, every 1 second, is shown.

11. Velocity Of Free Falling Object At Regular Time Intervals • The velocity increases. • How much does the velocity of the object increase by?

12. ACCELERATION vs. VELOCITY What will the acceleration of the ball be at t = 1s? t = 4s? At which time will velocity be the greatest?

13. Which variables affect the final velocity of free-falling objects? • Gravity • Time of fall

14. Solving one-dimensional problems dealing with vertical uniform acceleration. • A boy drops a ball from the roof of a house which takes 3.0 seconds to hit the ground. Calculate the velocity when the ball hits the ground.

15. Use your Kinematic Equations • Objects dropped from rest have a Vi of 0. • Given: Vi= 0m/s; a= -9.81m/s2t = 3.0s • Formula: Vf = Vi + at • Vf = -9.81 m/s2 ( 3.0s) • Vf = -29 m/s or 29 m/sdownward • The longer an object falls - the greater its velocity

16. Example #2 • A boy drops a ball from the roof of a house which takes 3.0 seconds to hit the ground. Calculate the distance the ball has traveled.

17. Answer • Given: t = 3.0s; a = -9.81 m/s2 • Find the correct kinematic equation • Δx = ½ at2 • = .5 (-9.8 m/s2) (3.0s )2 • =44m

18. CHECKPOINT • Page 64 #’s 1 and 3

19. FREE-FALL LAB • Step #1 • An egg dropped from a height of 6.20 m will have a final velocity of 12.8 m/s (neglecting air resistance) upon hitting the ground. Design an experiment to decrease the final velocity of the egg, and explain what effect air resistance has on a falling object’s final velocity. Be sure to calculate your egg’s final velocity. Extra Credit will be given to any group who lands their egg safely.

20. Air resistance does not depend upon the weight of the object. 6.7Falling and Air Resistance The amount of air resistance force an object experiences depends on the object’s speed and exposed surface area. 1. Speed The greater the speed, the greater the air resistance. 2. Exposed Surface Area The greater the surface area, the greater the air resistance.

21. This Week’s Schedule • Wednesday,Thursday and Friday– Work on Lab • Monday – Egg Drop • Egg Drop Rubric • Egg Drop On Time with Decreased Final Velocity -100 • Egg drop On Time with no Decreased Final Velocity – 94 • Egg drop Late with Decreased Final Velocity – 80 • Egg drop Late with no Decreased Final Velocity – 74 • Egg dropped with no effort - 50 • USE YOUR CLASS TIME WISELY!!!!!!!!!