# why do you weigh less on the moon Weight, mass and gravity
People often confuse mass and weight. Remember that weight is a force, and is measured in newtons. Mass is measured in kilograms (kg). The mass of an object is the amount of matter or "stuff" it contains. The more matter an object contains, the greater its mass. An elephant contains more matter than a mouse, so it has a greater mass. Mass is measured in kilograms, kg, or grams, g. A 100 kg object has a greater mass than a 5 kg object. Remember an object's mass stays the same wherever it is. All objects have a force that attracts them towards each other. This is called gravity. Even you attract other objects to you because of gravity, but you have too little mass for the force to be very strong. Gravity only becomes noticeable when there is a really massive object like a moon, planet or star. We are pulled down towards the ground because of gravity. The gravitational force pulls in the direction towards the centre of the Earth. Weight is a force caused by gravity. The weight of an object is the gravitational force between the object and the Earth. The more mass the object has the greater its weight will be. Weight is a force, so it's measured in newtons. On the surface of the Earth an object with a mass of 1 kg has a weight of about 10 N. The mass of an object stays the same wherever it is, but its weight can change. This happens if the object goes somewhere where gravity is stronger, or weaker, such as the Moon. The Moon has less mass than the Earth, so its gravity is less than the Earth's gravity. This means that objects weigh less on the Moon than they do on the Earth. The Moon's gravity is one sixth of the Earth's gravity. A 120 kg astronaut weighs 1200 N on Earth. On the Moon they would weigh only 200 N. The astronaut's mass is 120kg wherever they are. Since the force of gravity is proportional to the body s mass, and inversely proportional to the SQUARE of the body s distance from the object, the moon s gravity would generate (1/100) / (60 times as much force as earth s gravity on you. Thus it is approximately 1/360,000th as strong as earth s gravity. Given that the moon mass is roughly 1/100 of Earth s mass. If you were to stand on top of Mt Everest you would weigh roughly. 33% less. So technically yes you do weigh ever so slightly less when the moon is above you. This is how tides work. The tides are not affected by how hard the moon is pulling on the water directly under it. (Clearly, it isn t pulling hard enough to overcome the earth s gravity and lift the water straight up. ) Instead, the tides are caused by the DIFFERENCE in the moon s gravitational pull on water at different locations on the earth s surface. Specifically, these differences cause the water that is halfway between the nearest and farthest points on earth (from the moon s perspective) to flow ACROSS the earth s surface, either toward the near side or toward the far side, resulting in bulges in these two diametrically opposite locations, both of which experience high tide simultaneously.

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