Science ACE :

1. Science ACE : Thematic Studies on Gravity Around the Earth – Do we weigh lesser at the Earth’s equator than at the poles? Done By: Chua ZhongZhi(7) 1A2

2. Hypothesis • Hypothesis: Yes, we weigh lesser on the equator than at the poles.

3. What is Gravity? • Before we Investigate if we are heavier on the equator, we must understand what Gravity is. • Gravity is: • A force of attraction that exists between any two masses, any two bodies, or any two particles. • Not just the attraction between objects and the Earth. It is an attraction that exists between all objects, everywhere in the universe. • Gravity determines our weight and it varies depending on where we are on the Earth or Universe Video clip on gravity http://www.youtube.com/watch?v=0rocNtnD-yI

4. Earth’s Gravity • Earth's gravity, denoted g, refers to the acceleration that the Earth imparts to objects on or near its surface. • In its SI Unit, it is measured in m/s2. It has an approximate value of 9.81 m/s2. This quantity is informally known as little g. • The precise strength of the Earth's gravity varies depending on location. The nominal "average" value at the Earth's surface, known as standard gravity is, by definition, 9.80665 m/s2

5. Why do we weigh lesser at the equator? • Gravity is weaker nearer the equator because the Earth's rotation produces an apparent *centrifugal force. • *Centrifugal forcerepresents the effects of resistance of any physical object to a change in its state of motion that arise in connection with rotation and which are experienced as an outward force away from the centre of rotation. • Gravity provides *centripetal force, keeping objects on the surface moving in a circular motion. • * Centripetal force is a force that makes a body follow a curved path

6. Why do we weigh lesser at the equator? • Consider that if the gravity of the Earth were to shut off, objects would fly off into space in the direction of their motion in accordance with Newton's First Law of Motion. Alternatively, if Earth's gravity were weakened so as to match the centrifugal force, then objects there would appear to float. • Also, at the poles, only gravity would contribute to weight and objects would not float. In this sense, local gravity felt as weight is gravity due to the Earth's mass minus the centrifugal force.

7. Why do we weigh lesser at the equator • Another reason is the difference in gravity at different latitudes. The Earth's bulge which is around its equator causes objects at the equator to be farther from the planet's centre than objects at the poles. • Because the force due to gravitational attraction between two bodies (the Earth and the object being weighed) varies inversely with the square of the distance between them, objects at the equator experience a weaker gravitational pull than objects at the poles.

8. Why do we weigh lesser at the equator • In combination, the equatorial bulge and the effects of centrifugal force mean that sea-level gravitational acceleration increases from about 9.780 m per s−2 at the equator to about 9.832 m per s−2 at the poles, so an object will weigh about 0.5% more at the poles than at the equator.

9. Conclusion • Yes, we weight lesser at the Earth’s equator than at the poles

10. Thank You