1. Acceleration Due To Gravity
SPH3U

2. Make a Prediction
Your teacher will drop two objects of very different mass from the same height above the floor.
Predict which will hit the ground first.
You must write your prediction and explain your reasoning.

4. Observations
Observe the demonstration…

5. Explanation
Removing the resistance caused by the air (a fluid) results in the stunning observation that both objects accelerate at the same rate due to the force/pull of gravity.

6. Galileo’s Revelation…
Galileo Galilei performed experiments at the leaning tower of Pisa in Italy in the 16th century. He dropped objects of different masses from the tower and observed which hit the ground first.

7. Law of Falling Bodies
The accelerations due to gravity for object’s are different, not because of their masses, but rather because of air resistance caused by surface area, mass and volume differences.

8. Galileo's Experiment on the Moon

9. Law of Falling Bodies Galileo’s Experiments lead to the law:
In a vacuum (no air resistance) ALL objects accelerate at the same rate under the force of gravity.

10. Near the surface of the Earth it has been found that all objects accelerate at a rate of ag=g=9.8 m/s/s
Acceleration on Earth
The acceleration due to gravity on other stars and planets depends on the mass of the star or planet.
The more massive the star/planet the greater the pull of gravity on objects near it.

11. Comparison of accelerations
Some accelerations of gravity for some planets, moons and our star:
Earth: m/s/s
Moon: m/s/s
Jupiter: m/s/s
Sun: m/s/s

12. v2 = v1 + a∆t SAMPLE CALCULATIONS
Using one of the kinematics equations, determine the final speed for an object released from rest that falls for 3 seconds on
a) Earth b) Moon c) Jupiter d) Sun
v2 = v1 + a∆t