Transcript Gravity
Gravity 100 kg 5 kg 30 N 1. A chihuahua with a mass of 5 kg exerts a force of 30 N on a Happy Face with a mass of 100 kg. If the friction is 15 N, how fast did the chihuahua accelerate the Happy Face? 2. If the chihuahua pushes too far and they both fall off the edge of the table, which one accelerates faster? Gravity Objectives: • Describe 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. Gravity Gravity- an attractive force between two objects that depends on the masses of the objects and the distance between them Gravitational force increases as: Masses increase Objects move closer together Gravity Force of gravity increases as mass increases! Gravity Force of gravity increases as objects get closer together! Gravity Gravitational Acceleration (g): Gravity causes objects to accelerate toward the center of Earth. When all forces, except gravity, acting on a falling object can be ignored, the object is said to be in free fall. All objects near Earth’s surface would fall with the same acceleration. The acceleration of an object in free fall close to the Earth’s surface. g = 9.8 m/s2 • Weight- the gravitational force exerted on an object • Mass- measures the amount of matter – Weight and mass are related: — Weight (N) = mass (kg) x g (acceleration of gravity, m/s2) — How much would you weigh on the Moon? • Weight is different, but mass stays the same. Calculating Weight • WEIGHT ON EARTH W = 70 kg × 9.8 m/s2 = 686 N • WEIGHT ON THE MOON W = 70 kg × 1.6 m/s2 = 112 N Weight Calculator for the Solar System Why do all objects have the same free-fall acceleration? Newton’s second law shows that acceleration depends on both the force on an object and its mass. A heavier object experiences a greater gravitational force than a lighter object. However, a heavier object is also harder to accelerate because it has more mass. The extra mass of the heavy object exactly compensates for the additional gravitational force. Newton’s Law of Universal Gravitation or Did an apple really fall on his head? Projectile MotionAn object with horizontal velocity is pulled down by gravity. Gravity Centripetal ForceThe net force exerted toward the center of a curved path. – Car going around a curve – People on an amusement park ride – Earth’s gravity pulls the Moon into circular orbit Inertia Centripetal Force Gravity Centripetal Force“Centripetal” is not the name of a force – it actually describes a force. • Centripetal force may be due to : gravity — friction — a physical structure — Inertia Centripetal Force