the equation that links weight mass and gravitational field strength is weight equals mass times gravitational field strength which is w equals m times g where the unit of weight is newtons the unit of mass is kilograms and the units of gravitational field strength is newtons per kilogram also it can be meters per second squared because it's an acceleration so this is planet earth and a person has a mass of 100 kilograms gravitational field strength on earth is 9.8 newtons per kilogram so what is the person's weight so the person's weight is going to be calculated using the equation weight equals mass times gravitational field strength w equals m times g so we use the equation as it is because we're working out w weight so weight equals 100 kilograms times 9.8 newtons per kilogram which gives you a weight of 900 980 newtons so the weight of this person on earth is 980 newtons it's question time attempt these questions to check your understanding so the person now goes to mars person's mass is still 100 kilograms however the gravitational field drink on mars is 3.7 newtons per kilogram nearly three times less than enough so to calculate the person's new weight you simply use w equals m times g weight equals mass times gravitational field strength whereby weight equals 100 kilograms times 3.7 newtons per kilogram and that will then give you a weight of 370 newtons so weight and gravitational field strength are directly proportional so if you increase the gravitational field strength you are going to have an increased weight if you lower the gravitational field strength you are going to decrease the person's weight and weight and mass are also directly proportional this is the problem you will learn how to solve press pause to attempt it the method and the answer will follow so these two people person a and b are on earth remember earth has a gravitational field strength of 9.8 newtons per kilogram so we have their weights person a's weight is 680 newtons person b's weight is 470 newtons so because we've got the gravitational field strength of earth at 9.8 newtons per kilogram and we've got their weights we can use this information to calculate their masses so for person b we use the equation weight equals mass times gravitational field strength so now we substitute in the numbers 470 newtons equals mass times 9.8 newtons per kilogram so now we rearrange for m mass so mass equals 470 newtons divided by 9.8 newtons per kilogram that will give you a mass of 47.9 kilograms so this person's weight is 470 newtons but their mass due to the gravitational filtering on earth is 47.9 kilograms person a's weight is 680 newtons so they substitute in the data so 680 newtons equals mass times 9.8 newtons per kilogram you now need to rearrange the equation for mass so now mass equals 680 newtons divided by 9.8 newtons per kilogram that gives you a mass of 69.4 kilograms 69 69.4 kilograms it's question time attempt these questions to check your understanding press pause to practice using those keywords the answers will follow press pause to go through your answers and make any corrections to your mistakes press pause to answer the questions the answers will follow and if you're stuck just re-watch the video press pause to go through your answers and make any corrections to your mistakes visit ksites.com for more free videos worksheets and quizzes at kscience.com and don't forget to like and subscribe