Transcript Gravity
Topic: Forces and Motion Aim: How does gravity act on objects? Do Now: Take out your HW ditto. http://www.brainpop.com/science/motionsforcesandtime/newtonslawsofmotion/ HW: Ditto – Newton’s Laws of Motion 1 2 3 4 • Force of attraction Gravity between all objects in the universe Newton’s Law of Universal Gravitation • A force of gravity acts between all objects in the universe. • Gravity increases as mass increases • Gravity decreases as distance increases Weight • Measure of the force of gravity on an object • W = mass x ag –ag = 9.8 2 m/s For every second an object falls, its velocity increases by 9.8m/s Suppose that an elephant and a feather are dropped off a very tall building from the same height at the same time. Suppose also that air resistance could be eliminated such that neither the elephant nor the feather would experience any air drag during the course of their fall. Which object - the elephant or the feather - will hit the ground first? In the absence of air resistance, the elephant and the feather strike the ground at the same time. • Ex: How much does a 50kg person weigh on Earth? –W = m x a –W = (50kg) (9.8 m/s2 ) –W = 490.0N –(By the way, 4.55N = 1lb) Let’s summarize… 1. Describe gravity. 2. State Newton’s law of universal gravitation. 3. Explain the relationship between gravity and mass. 4. Explain the relationship between gravity and distance. 5. Describe weight. 6. State the formula that can be used to determine an object’s weight. 7. What is the acceleration due to gravity? http://www.brainpop.com/science/motionsforcesandtime/gravity/ http://www.youtube.com/watch?v=CfchR2EseD0 http://www.youtube.com/watch?v=gjfLI7aJKmQ The moon has a smaller mass than the earth. If you were able to travel to the moon, your weight would 1. increase 2. decrease 3. remain the same 4. vary from day to night The force of gravity on an object depends primarily on the object’s 1. density 2. momentum 3. mass 4. volume The distance of the star Vega from Earth is 1.6 million times greater than the distance from the sun to the Earth. Which of the following best describes the gravitational influence of Vega on Earth? 1. It is roughly equal to that of the sun. 2. Its influence is greater than that of the sun. 3. Its influence is small because of its distance. 4. It influences the magnitude of Earth’s mass. If a solid object is taken from Earth far into space, which of the following measurements of the object will change the most? 1. density 2. mass 3. volume 4. weight If you were able to go to the top of a building and simultaneously drop an apple and a basketball , they would hit the ground at the same instant because 1. the force of gravity on them is equal 2. they have the same mass 3. air resistance on both is the same 4. they have the same amount of kinetic energy As a bike rider goes up a hill, the force of gravity acts to 1. increase the weight of the rider 2. increase the acceleration of the rider 3. decrease the weight of the rider 4. decrease the speed of the rider How would the measureable properties of a golf ball change if it were moved from the earth to the moon? 1. It would have the same weight but different mass. 2. It would have the same mass but different weight. 3. It would have the same density but different mass. 4. It would have the same mass but different density. The moon orbits the earth at a speed of approximately 1 kilometer per second. The moon is kept in orbit by which of the following? 1. Lunar phases 2. Magnetism 3. Gravity 4. Ocean tides Which of the following cause a ship’s iron anchor to sink to the ocean floor when released overboard? 1. Nuclear forces 2. Magnetism 3. Gravity 4. Chemical forces Which of the following statements best describes the force of Earth’s gravity on a rocket moving upwards? 1. The gravitational force is constant at all altitudes. 2. The gravitational force is weaker when the rocket is higher. 3. The gravitational force is stronger when the rocket is higher. 4. The gravitational force is zero when the altitude is greater than 10, 000 miles. Which of the following statements describes a result of Earth’s gravitational force on the moon? 1. The Moon has craters. 2. The Moon orbits around the Earth. 3. The Moon lacks an atmosphere. 4. The Moon has less gravity than the earth.