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9J Gravity and Space Mass and weight • What is gravity? • What is weight? What units is it measured in? • What is mass? What units is it measured in? • How could you change your weight? • How could you change your mass? True or false? • • • • • • • • • • • If the earth stopped spinning we would float into space. There is no gravity on the moon. NASA have an anti-gravity room where gravity can be turned off and people can float. It is possible to shield the force of gravity by using lead or other materials. Isaac Newton discovered gravity. Nottingham Forest football team won the Champions league in 1979 and 1980. You have no mass in space. There is no gravity in space because you are far from the earth. Weight is measured in kilograms. There is no gravity in space because space is a vacuum. If we could suck all the air out of the classroom, we would float around. All false! • • • • • • • • • • • Only this one is true! If the earth stopped spinning we would float into space. There is no gravity on the moon. NASA have an anti-gravity room where gravity can be turned off and people can float. It is possible to shield the force of gravity by using lead or other materials. Isaac Newton discovered gravity. Nottingham Forest won the Champions league in 1979 and 1980. You have no mass in space. There is no gravity in space because you are far from the earth. Weight is measured in kilograms. There is no gravity in space because space is a vacuum. If we could suck all the air out of the classroom, we would float around. Gravity What is gravity? Gravity Gravity is a force between ALL objects! Gravity Gravity Gravity is a very weak force. The force of gravitational attraction between Mr Porter and his wife (when 1 metre apart) is only around 0.0000004 Newtons! Gravity The size of the force depends on the mass of the objects. The bigger they are, the bigger the force! Small attractive force Bigger attractive force Gravity The size of the force also depends on the distance between the objects. Gravity We only really notice the gravitational attraction to big objects! Hola! ¿Como estás? Gravity The force of gravity on something is called its weight. Because it is a force it is measured in Newtons. Weight Gravity On the earth, Ms Stamp’s weight is around 700 N. I love physics! 700 N Gravity On the moon, her weight is around 110 N. Why? 110 N Astronauts on the moon Gravity In deep space, far away from any planets or stars her weight is almost zero. (She is weightless). Why? Cool! Mass Mass is a measure of the amount of material an object is made of. It is measured in kilograms. Mass Ms Stamp has a mass of around 67 kg. This means he is made of 67 kg of blood, bones, hair and poo! 67kg Mass On the moon, Ms Stamp hasn’t changed (she’s still Ms Stamp!). That means she still is made of 67 kg of blood, bones, hair and poo! 67kg Gravity In deep space, Ms Stamp still hasn’t changed (she’s still Ms Stamp!). That means she still is made of 77 kg of blood, bones, hair and poo! I feel sick! 67kg Mass and weight Mass is a measure of the amount of material an object is made of. It is measured in kilograms. Weight is the force of gravity on an object. It is measured in Newtons. Weight and Mass Experiment • You are going to investigate the relationship between mass and weight. • Aim: • Prediction: • Variables: (independent, dependent, control) Mass (g) Mass (kg) Weight (N) Calculating weight • How do you calculate weight? • What is the gravitational field strength on The Earth? Calculating weight The force of gravity on one kilogram is called the gravitational field strength. It s measured in Newtons per kilogram (N/kg) Calculating weight To calculate the weight of an object you multiply the object’s mass by the gravitational field strength wherever you are. Weight (N) = mass (kg) x gravitational field strength (N/kg) Example The gravitational field strength on earth is around 10 N/kg. What is your weight if your mass is 45 kg? Weight (N) = mass (kg) x gravitational field strength (N/kg) Weight (N) = 45 kg x 10 N/kg Weight = 450 N The Universe • Name the main objects in our solar system • What is the name of our galaxy? • How do we measure distances in space? Put the cards in order of size Our solar system Moons in the solar system Distances between the planets to scale http://www.northernstars.com/solar_system_distance_scal.htm Our place in the universe Satellites • What is a satellite? • Name a natural satellite of The Earth. • Name a natural satellite of The Sun. • Name an artificial satellite of The Earth. Video http://lgfl.skoool.co.uk/content/keystage3/Phy sics/pc/learningsteps/STLLC/launch.html Artificial Satellites • What do we use artificial satellites for? Artificial satellites • Among other jobs, artificial satellites orbiting the Earth are used for: – telecommunications (transmitting information between distant parts of the Earth) – satellite navigation systems (‘satnav’) – spying on other countries, and – weather forecasts. Weather • A weather satellite is primarily used to monitor the weather and climate of Earth. • Satellites can be either polar orbiting, seeing the same swath of the Earth every 12 hours • Or geostationary, hovering over the same spot on Earth by orbiting over the equator while moving at the speed of the Earth's rotation Spying • A spy satellite or reconnaissance satellite observes the Earth • They can also be used to listen to communications and are deployed for military or intelligence applications. Sat Nav • The Global Positioning System (GPS) is a spacebased system that provides reliable location information in all weathers and at all times • In car sat nav systems receive data from up to four satellites giving accurate positioning • Can be used anywhere on or near the Earth when there is an unobstructed line of sight to four or more GPS satellites. Telecommunications • Communications satellites occupy a geostationary orbit. • They are in orbit above the equator at just the right distance so that it takes them one day to complete an orbit. • As a result, they always appear in the same position when seen from the ground. • This is why satellite television dishes can be bolted into position and do not need to move. Satellite orbits • http://youtu.be/E4k3kEA3pmo Using satellites to view space Astronomical satellites, such as the Hubble Space Telescope (HST), are large telescopes placed in a high orbit far from the effects of the Earth’s atmosphere. These satellites can ‘see’ much further into space and give us images of stars and galaxies many light years away, like this cartwheel galaxy.
