Transcript Ch.9 Gravity

9 Gravity
• Homework
• RQ: 2, 4, 5, 6, 9, 17, 22.
• Exs: 3, 4, 10.
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Intensity
• intensity = power/area
• SI Unit: watts/m2
• Example: the brightness of this screen is
determined by the projector-power and the
size of the screen
2
Inverse-Square Relations
3
Inverse Proportional
• independent variable doubles and
dependent variable halves.
• Ex. For constant Net-Force of 10N.
• Mass1 = 1kg Accel1 = 10N/1kg = 10m/s/s
• Mass2 = 2kg Accel2 = 10N/2kg = 5m/s/s
4
Inverse-Square Proportional
• independent variable doubles and
dependent variable quarters.
• Ex. Distance = 1m, Force = 64N.
• Distance = 2m, Force = 16N.
• Distance = 4m, Force = 4N.
• Distance = 8m, Force = ?.
• /
5
gravitational force
• Newton’s Synthesis: all matter is weakly
attracted.
• Cavendish Experiment
• Torsion Balance
m1m2
F G 2
d
6
differential pull of gravity
• Closer parts of objects more strongly
attracted
• differential pull causes tides
• Tides larger at full and new moon
7
Summary
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Inverse relations,
Inverse-square relations,
How to test for,
Examples of each,
And differential pull.
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