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15801257.ppt

  1. 1. •A FORCE is a push or a pull. •GRAVITY is a force that pulls objects toward one another. It pulls objects towards Earth. •Try jumping in the air. What happens? Gravity pulls you back to Earth.
  2. 2. This boy is going down a slide. GRAVITY is pulling him towards Earth. The slide keeps him from falling straight down.
  3. 3. This penguin is jumping off of a cliff. It doesn’t float up, and it does not stay in the air. GRAVITY is pulling the penguin down into the water.
  4. 4. What are some other real-world examples of gravity in action? What have you experienced?
  5. 5. Weight Weight is the measure of the gravitational force on an object. • weight is a force measured in newtons (N) Changes depending on the acceleration due to gravity acting on the object. You weigh less on the Moon because there is less gravity.
  6. 6. Weight Formula Units: W = weight in newtons (N) m = mass in kilograms (kg) g = acceleration due to gravity (m/s2) weight (w) = mass (m) X gravity (g)
  7. 7. Acceleration Due to Gravity (g) An object falling (on Earth) has an acceleration due to gravity (g) of 9.8 m/s2. All objects near the surface of the Earth fall with the same rate of acceleration https://www.youtube.com/watch?v=E43-CfukEgs
  8. 8. Air Resistance •Type of fluid friction (doesn’t have to be liquid, can be air) •Causes things to reach a terminal velocity – when the force of the air resistance and the weight of an object are equal and balanced forces, so things are not accelerating, but moving at a constant velocity toward the ground.
  9. 9. Air Resistance (cont.) •heavy objects have a higher terminal velocity than lighter objects •Things that have a bigger surface area will have a lower terminal velocity that things with a smaller surface area.
  10. 10. You know that gravity is a force. Other forces can oppose, or act against, gravity. Think of catching a ball. Your hand stops the ball from falling to the ground. This means gravity has been opposed.
  11. 11. Think of a rocket as it launches into the sky. The rocket is working against Earth’s gravity. It is going upwards instead of falling to the ground.
  12. 12. What are some other real-world examples of gravity being opposed? What have you experienced?
  13. 13.  An object must travel 7 miles a second to escape Earth’s gravitational pull.  Although gravity is a force, it always pulls; gravity will never push.  Gravity keeps the Moon around the Earth, and the Earth around the Sun. This is because each has its own gravitational force pulling one another.

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