1 / 17

PHYSICAL SCIENCE

PHYSICAL SCIENCE. Chapter 3 Forces 3.2 Gravity. 3.2 Gravity Objectives. Describe the gravitational force. Distinguish between mass and weight. Explain why objects that are thrown will follow a curved path. Compare circular motion with motion in a straight line. What is Gravity.

mccollumm
Download Presentation

PHYSICAL SCIENCE

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. PHYSICAL SCIENCE Chapter 3 Forces 3.2 Gravity

  2. 3.2 Gravity Objectives • Describe the gravitational force. • Distinguish between mass and weight. • Explain why objects that are thrown will follow a curved path. • Compare circular motion with motion in a straight line.

  3. What is Gravity • Gravity is an attractive force between any two objects that depends on the masses of the objects and the distance between them. • As the mass of either object increases, so does the gravitational force between them. • Gravitational force between two objects increase as the distance between them decreases.

  4. What is Gravity • Gravity is one of the four basic forces… • Gravity • Electromagnetic force • Strong force • Weak force http://scienceblogs.com/startswithabang/2012/06/27/the-strong-force-for-beginners/ http://mail.colonial.net/~hkaiter/Gravity_Inertia.html

  5. The Law of Universal Gravitation • The Law of Universal Gravitation by Sir Isaac Newton, 1687 gravitational force = (constant) • (mass 1) • (mass 2) (distance)2

  6. The Law of Universal Gravitation • “F” is the force of gravity. • “G” is a constant called the universal gravitational constant. • “m1” and “m2” are the masses. • “d” is the distance between the two masses. • Gravity is a long range force that gives the universe its structure. • Gravitational force never completely goes to 0 between any two objects.

  7. The Law of Universal Gravitation • In the 1840s, the most distant planet known was Uranus. • The observed motion of Uranus and the calculated motion of Uranus according to the law of universal gravitation differed slightly. • Some astronomers attributed this to an undiscovered planet. • Two astronomers independently calculated the orbit of this undiscovered planet and, as a result, Neptune was discovered in 1846.

  8. http://imgarcade.com/1/king-neptune-drawing/

  9. http://universeandplanets.blogspot.com/2011/07/neptune-planet.htmlhttp://universeandplanets.blogspot.com/2011/07/neptune-planet.html

  10. Earth’s Gravitational Acceleration • Due to inertia, all objects fall with the same acceleration regardless of mass. • Close to Earth’s surface, the acceleration of a falling object in free fall is about 9.8 m/s2. • This acceleration constant is sometimes given the symbol “g” and called the acceleration of gravity. force of gravity (N) = mass (kg) x acceleration of gravity (m/s2) F=mg • The gravitational force on a skydiver with a mass of 60 kg would be…. F = mg = (60 kg)•(9.8 m/s2) = 588 N

  11. Earth’s Gravitational Acceleration • Mass is a measure of the amount of matter in an object and weight is the gravitational force of attraction exerted on an object. • Acceleration of gravity on the Moon is 1.6 m/s2 – about 1/6th as large as Earth’s gravitational acceleration. http://science.nasa.gov/science-news/science-at-nasa/2009/17jul_discoveringearth/

  12. Weightlessness and Free Fall • Typical shuttle mission orbits Earth at an altitude of about 400 km. • At 400 km, the force of Earth’s gravity is about 90% as strong as it is at Earth’s surface. • A space shuttle in orbit is in free fall, but it is falling around Earth instead of straight down. • Everything in the shuttle is falling around Earth at the same rate as the shuttle itself. • This creates the sensation of weightlessness. • Next slide - http://hrsbstaff.ednet.ns.ca/jenninj2/Physics%2012/Gravitation/universal_gravitation.htm

  13. Projectile Motion • Projectiles don’t travel in straight lines, their path curves downward due to gravity. • The force we exert on a thrown ball gives it horizontal motion. • After the ball is released, no force accelerates it forward, so its horizontal velocity is constant (excluding air resistance). • When the ball is released, gravity pulls it downward, giving it vertical motion.

  14. Projectile Motion • Now the ball has constant horizontal velocity, but increasing vertical velocity. • Gravity exerts an unbalanced force on the ball, changing the direction of its path from only forward to forward and downward. • Thrown ball and dropped one hit the ground at the same time. • Both balls travel the same vertical distance in the same amount of time, though the thrown ball travels a greater horizontal distance than the dropped ball.

  15. Centripetal Force • Acceleration toward the center of a curved or circular path is called centripetal acceleration. • The net force exerted toward the center of a curved path is called a centripetal force. • Anything that moves in a circle is doing so because a centripetal force is accelerating it toward the center. • Earth’s gravity exerts a centripetal force on the Moon that keeps it moving in a near circular orbit.

  16. Video Links • Brian Cox visits the world's biggest vacuum chamber - Human Universe: Episode 4 Preview - BBC Two (4:41) - https://youtu.be/E43-CfukEgs • Zero Gravity Flight - Weightlessness (4:58) - https://youtu.be/HQbAwE83phk

More Related