[Music] hi and welcome back to fre science lessons. co.uk by the end of this video you should be able to calculate the amount of gravitational potential energy gained by an object raised above ground level so we're going to stop by looking at what's meant by gravitational potential energy gravitation potential energy is the energy stored in an object due to its position above the Earth's surface and this is due to to the force of gravity acting on an object we're going to start by looking at a simple example this shows a ball sitting on the ground I'm now going to lift the ball off the ground and place it on a shelf like this to do this I'm using the chemical energy store on my muscles and I'm changing this to gravitational potential energy in the ball so the ball now has a store of gravitational potential energy if I now allow the ball to fall off the shelf back to the ground like this then the store of gravitational potential energy is now changed to other forms of energy such as thermal energy and kinetic energy so the ball now has no gravitational potential energy we can calculate the gravitational potential energy of an object by using this equation the gravitational potential energy in Jews equals the mass in kilograms multiplied by the gravitational field strength multiplied by the height in meters the gravitational field strength is a measure of the force of gravity and this value will be given in the question now you are not given the equation for gravitational potential energy in the exam you've got to make sure that you learn it okay let's take a look at a sample question a crane lifts a 75 kilogram Mass a height of 8 m calculate the gravitational potential energy gained by the mass the value of the gravitational field strength is 9.8 Newtons per kilog so here's the equation we're going to use the mass of the object is 75 Kg the gravitational field strength is 9.8 Newtons per kg and the height is 8 m putting these numbers into the equation gives us a gravitational potential energy of 5,880 Jew here's a question for you to try a ball with a mass of 500 G is lifted onto a shelf which is 1.5 m above the ground calculate the gravitational potential energy gained by the ball pause the video now and try this yourself okay here's the equation that we're using the mass is 500 G so first we've got to convert this to kilog by dividing by 1,000 500 G is No.5 kilog the value of the gravitational field strength is 9.8 Newtons per kilogram and the height is 1.5 M putting these numbers into the equation gives us a value for the gravitational potential energy of 7.35 jewles remember you'll find plenty more questions on gravitational potential energy in my Vis Vision workbook and you can get that by clicking on the link above okay so hopefully now you should be able to calculate the amount of gravitational potential energy gained by an object raised above ground [Music] level