1. An Introduction to Acceleration: More Practice

2. An Introduction to Acceleration: More Practice

3. An Introduction to Acceleration: More Practice

4. An Introduction to Acceleration: More Practice

5. An Introduction to Acceleration: More Practice

6. An Introduction to Acceleration: More Practice

7. Gravity

8. Read “Going Ballistic”
Key Points:
There is gravity between all objects with mass
Whenever we throw an object, it travels in a parabola
If it never hit the ground, the shape would be an ellipse

9. Definitions Mass Weight the amount of matter in an object
Measured in kg
Weight
The amount of gravitational force acting on an object
Measured in N

10. Newton’s Law of Gravitational Attraction
There is a force of gravity between any two objects with mass
Larger distance between them, smaller force

11. g = 9.8 m/s2 [down] The acceleration due to the Earth’s gravity is
The magnitude of this acceleration is denoted by the letter g.

12. Do all objects fall at the same rate?
Is there anything that can affect the rate they accelerate?

13. Mass doesn’t matter
No matter what your mass, everything falls at the same rate if we ignore air resistance
Galileo is attributed with this discovery
Video

14. Drag
However, some objects are slowed by atmospheric drag more than others.

15. Terminal velocity
At a given speed, the drag will equal the gravity, and the object will stop accelerating, i.e. reach “terminal velocity.”

16. Terminal velocities Typical terminal velocities:
Human m/s (190 km/h)
Human with parachute 5 m/s (18 km/h)
Dandelion seed m/s (1.8 km/h)

17. The fastest man
On August 16th, 1960 U.S. Air Force Captain Joe Kittinger broke the sound barrier (1240 km/h) during a free-fall from the high altitude balloon Excelsior III, at an altitude of approximately 31 km.

18. Highest fall survived (without a parachute)
Flight attendant Vesna Vulovič fell 10,000 m on January 26, 1972 when she was aboard a plane that was brought down by explosives over the Czech Republic.
She suffered a broken skull, three broken vertebrae (one crushed completely), and was in a coma for 27 days, but she survived!

19. g’s
Accelerations are often given in terms of g.
For example,

20. Blackout
A typical person can handle about 5 g before loss of consciousness, “blackout,” occurs.
The record for the most g forces on a roller coaster belongs to Mindbender at Galaxyland Amusement Park in Edmonton, Alberta, at 5.2 g.

21. Greyout
Through the combination of special g- suits and efforts to strain muscles — both of force blood back into the brain— modern pilots can typically handle 9 g or more.
They may experience a “greyout” (temporary loss of colour vision, tunnel vision, or an inability to interpret verbal commands) between 6 and 9 g.

22. Negative g’s
Resistance to "negative" or upward g’s, which drive blood to the head, is much less (typically in the -2 to -3 g range).
During “redout,” vision goes red, probably due to capillaries in the eyes bursting under the increased blood pressure.

23. “g-Force” Acceleration perpendicular to the spine is more tolerable.
Acceleration pushing the body backwards (“eyeballs in”) is tolerable up to 17g, and pushing the body forwards (“eyeballs out”) up to 12g.

24. Strongest g-forces survived
Voluntarily: Colonel John Stapp in sustained 46.2 g in a rocket sled, while conducting research on the effects of human deceleration

25. Strongest g-forces survived
Involuntarily: Formula One racing car driver David Purley survived an estimated 178 g in when he decelerated from 173 km/h to 0 in a distance of 66 cm after his throttle got stuck wide open and he hit a wall

26. Everyday g-forces
Coughing: 3.5 g
Sneezing: 2.9 g

27. Free fall Objects in free-fall feel 0 g, or “weightlessness.”
There is no such thing as zero gravity, gravity acts on you everywhere in the universe

28. Fg = mg Where, Fg – Force of Gravity (N) m – mass (kg)
On Earth,
Fg = mg
Where,
Fg – Force of Gravity (N)
m – mass (kg)
g – Gravitational Field Strength (N/kg) or acceleration due to gravity (m/s2)
g = 9.8 m/s2 [down]
or 9.8 N/kg[down]

29. Example:
Andrew has a mass of 68 kg, what is his weight?

30. What is the mass of this ________?

31. Homework
Gravitational field strength worksheet