Microgravity

Gravity Gravity is an attractive force between two bodies based on their mass and distance. This is known as the gravitational force an object exerts. F=G(m1*m2/R2) Acceleration due to gravity is the rate at which objects subject to gravity will fall g = G*mEarth/R2 F = Gravitational Force G = Gravitational constant (6.67300 × 10-11 m3 kg-1 s-2) m1 & m2 refer to the masses of 2 bodies measured in kg R= Distance between bodies measured in meters g = 9.81m/s2

Microgravity Microgravity refers to a small amount of gravity approaching and including zero-gravity. There is microgravity in space. Microgravity is related to free-fall. When objects fall at the same acceleration due to gravity (9.8m/s2 or 1g) Roller coaster? Newton’s thought experiment Simulated microgravity The condition of microgravity comes about whenever an object is in free fall. That is, it falls faster and faster, accelerating with exactly the acceleration due to gravity (1g). As soon as you drop something (like an apple) it is in a state of free fall. The same is true if you throw something; it immediately starts falling towards Earth. Newton developed a thought experiment to demonstrate this concept. Imagine a mountain so high that its peak is above the atmosphere of the earth. Imagine on top of that mountain a cannon, that fires horizontally. As more and more charge is used with each shot, the speed of the cannonball will be grater, and the projectile will impact the ground farther and farther from the mountain. Finally, at a certain speed, the cannonball will not hit the ground at all. It will fall toward the circular earth just as fast as the earth curves away from it. In the absence of drag from the atmosphere, it will continue forever in an orbit around the earth. This was the first and best explanation of what an orbit is. An object in orbit is weightless not because 'it is beyond the earth's gravity' but because it is in 'free-fall' - just like a skydiver. The difference is that it has enough horizontal speed never to hit the ground. Simulated microgravity – NASA’s “Vomit Comet” is the plane that flies in parabolas which simulates microgravity up to 25 seconds. NASA also has vacuum drop towers where tests can be performed.

Inverse Square Law Formula Fgrav ~ 1/d2 Where d = distance in meters Since distance is raised to the 2nd power, it is said that the force of gravity is inversely related to the square of the distance. If Fgrav goes up, then distance goes down. If distance goes up, then Fgrav goes down. Because distance is squared, changes in distance have a large affect.

Let’s Break it Down! Fgrav ~ 1/d2 Take out your calculators. Complete the table on your worksheet to see how much gravity is reduced as distance increases or decreases! Fgrav ~ 1/d2 1/22 = ¼ = 0.25 = 25% 1/32 = 1/9 = 0.11 = 11% 1/42 = 1/16 = 0.063 = 6.3% 1/52 = 1/25 = 0.04 = 4% 1/62 = 1/36 = 0.03 = 3% 1/72 = 1/49 = 0.02 = 2% 1/82 = 1/64 = 0.015 = 1.5% 1/92 = 1/81 = 0.012 = 1.2% 1/102 = 1/100 = 0.01 = 1%

Let’s Practice! Work alone or in pairs to complete the questions on your worksheet. Review as a class.

Closing it up… Complete the exit ticket and turn it in before you leave class!