1. GRAVITATIONAL FORCE Attraction of Matter

3. G RAVITATIONAL F ORCE Gravitational force (F g ) is the force that attracts any two objects together.  Gravitational force is an example of a force that acts on objects whether  or not they actually touch each other, even if the objects are in a vacuum.  These forces are referred to as action-at-a- distance forces.

4. G RAVITATIONAL F ORCE  An influence on a suitable object over a region of space, whether it is an attraction or a repulsion, as a field  This region of influence of gravitational force due to an object is a gravitational field.

5. G RAVITATIONAL F ORCE The gravitational field strength is defined as the gravitational force per unit mass:

6. G RAVITATIONAL F ORCE The gravitational field strength is defined as the gravitational force per unit mass:

7. G RAVITATIONAL F ORCE  The gravitational field strength is inversely proportional to the square of the distance.

8. W EIGHT VS. M ASS  The weight of an object is the force of gravity acting on the object.  The symbol for weight is therefore also F g.  Since weight is a force, it is measured in (N).  Mass, on the other hand, is a scalar that relates to the quantity of matter an object contains.  It is measured in kilograms (kg).

9. W EIGHT VS. M ASS

10. G RAVITATIONAL F ORCE

11. U NIVERSAL G RAVITATION  Gravity affects all masses in the universe.  No matter where you are on Earth or in outer space, you exert a gravitational force on every object  every object exerts a gravitational force, of equal magnitude but opposite direction, on you.  Because gravitational force acts over any distance, the range of its effect is infinite.

12. U NIVERSAL G RAVITATION Newton’s law of universal gravitation: 6,371 km

13. U NIVERSAL G RAVITATION

14.  Mount Logan in the Yukon is 5959 m above sea level, and is the highest peak in Canada. Earth’s mass is 5.97x10 24 kg and Earth’s equatorial radius is 6.38x10 6 m. What would be the difference in the magnitudes of a 55.0-kg person’s weight at the top of the mountain, and that person’s weight at sea level ? Assume that Earth’s equatorial radius is equal to the distance from Earth’s centre to sea level.