Explain like I’m 5. Ok I’m confused. If I “weigh” 100 lbs on earth it is due to the pull of the earths gravity on my body. But in space I’d be weightless. So how do you calculate mass of something in space ? All this thought because of the new toilet going up to the space station !!!
In: Physics
One way to work out the mass of an object is to use springs. Mass makes it difficult to change an object’s *velocity* – the speed and direction it is moving in. The amount of force required is directly proportional to it’s mass. So if something is twice as massive, it takes twice the force to accelerate it. By pushing and pulling objects via springs, we can see how much the spring stretches or compresses, and use that to calculate mass.
On Earth, we are used to the additional gravitational force. In fact, weight is literally the force of attraction between an object and Earth because of gravity. In the imperial system, pounds can be a unit of mass *or* of force. This means that an object that *weighs* 100lbs has a mass of 100lbs, and also that the gravitational force on that object at Earth’s surface is 100lbs. But if you took that object to the moon, the mass would be the same but the weight would change. It could have two different amounts of pounds depending on what you meant!
In metric/SI, we use kilograms for mass and Newtons for force. This avoids that issue. An object has a certain mass in kg, which is fixed. The weight in N can change depending on gravity.
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