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Contents

• Introduction• Universal laws of gravity• Earth’s Gravity• Applications of gravity• Reference

Introduction

Introduction

• Gravity, is one of the four fundamental interactions of nature, along with strong interaction, electromagnetic force and weak interaction.

Definition of Gravity

• The state of having weight; beaviness; as, the gravity of lead.

• The tendency of a mass of matter toward a center of attraction; esp., the tendency of a body toward the center of the earth; terrestrial gravitation.

Introduction

• Modern physics describes gravitation using the general theory of relativity, in which gravitation is a consequence of the curvature ofspacetime which governs the motion of inertial objects.

• The simpler Newton's law of universal gravitation provides an accurate approximation for most calculations.

Universal laws of gravity

Universal laws of gravity

• The Center of Mass for a Binary System• We may define a point called the center of

mass between two objects through the equations

Universal laws of gravity

• Newton's Modification of Kepler's Third Law• Newton proposed that both the planet and

the Sun orbited around the common center of mass for the planet-Sun system. He then modified Kepler's 3rd Law to read.

• P is the planetary orbital period and the other quantities have the meanings described above, with the Sun as one mass and the planet as the other mass.

Universal laws of gravity

• Two Limiting Cases• The center of mass for the system essentially

concides with the center of the massive object

• This is the situation in the Solar System: the Sun is so massive compared with any of the planets that the center of mass for a Sun-planet pair is always very near the center of the Sun.

Universal laws of gravity

• Weight and the Gravitational Force• It plays a part in dynamics, where W equals to

MG, which brings in newtons 3 laws

Earth’s Gravity

Earth’s gravity

• Every planetary body (including the Earth) is surrounded by its own gravitational field, which exerts an attractive force on all objects.

• The strength of the gravitational field is numerically equal to the acceleration of objects under its influence, and its value at the Earth's surface, denoted g, is approximately expressed below as the standard average.

Earth’s gravity

• Standard average-g = 9.81 m/s2 = 32.2 ft/s2

• Ignoring air resistance, an object falling freely near the Earth's surface increases its velocity with 9.81 m/s (32.2 ft/s or 22 mph) for each second of its descent.

Earth’s gravity

• the Earth itself experiences an equal and opposite force to that acting on the falling object, meaning that the Earth also accelerates towards the object .

• However, because the mass of the Earth is huge, the acceleration of the Earth by this same force is negligible, when measured relative to the system'scenter of mass.

Applications of Gravity

Applications of Gravity

Education• Acceleration at a Height• Acceleration at a Depth• Comparison of acceleration due to gravity• Rotation of Earth• Comparison of gravitational acceleration• Rate of change of gravity

Applications of Gravity

Daily life• Gravity chair• Gravity skateboard

Reference

• http://en.wikipedia.org/wiki/Gravitation• http://www.howstuffworks.com/question23

2.htm• http://csep10.phys.utk.edu/astr161/lect/hist

ory/newtongrav.html• http://www.google.com.sg/search?hl=en&q=

definition+of+gravity&aq=0c&aqi=g-c2g-sx1g-c1g-sx1g-c1g-sx1g-c3&aql=&oq=definition+ofgravity&gs_rfai=

• http://www.thefreedictionary.com/gravity• http://www.brainyquote.com/words/gr/gravi

ty170416.html• http://www.google.com.sg/imglanding?q=Ph

ysics%20gravity&imgurl=http://gravitationalpull.net/wp/wp-content/uploads/2007/07/blackhole_diagram.jpg&imgrefurl=http://gravitationalpull.net/wp/%3Fpage_id%3D193&usg=__mZfjkEG1Dwab3DTjivPwkaKRSc0=&h=1024&w=1024&sz=45&hl=en&itbs=1&tbnid=PHCYIcafIdhCFM:&tbnh=150&tbnw=150&prev=/images%3Fq%3DPhysics%2Bgravity%26hl%3Den%26sa%3DG%26gbv%3D2%26tbs%3Disch:1&sa=G&gbv=2&tbs=isch:1&start=0

• Thank you