# Physics THRUST

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To begin I just need to know how to do thrust.

A lunar lander in powered descent at 100 m above the surface of the moon slows down from a velocity of 20 m/s to 0.5 m/s at constant acceleration. Assume that the lander has a mass of 20,000 kg and that burning the fuel does not change the mass. Answer the following questions.

What is the acceleration of the lander?
We know that the formula for gravitational acceleration due to gravity is g= G X M/R^2
We know G is a constant called universal gravitational constant which is equal to 6.67 x 10^-11 N* m^2/kg^2. M is the mass of the object in which the gravitational acceleration is being found. R is the radius of the object. There is a negative sign in front of the equation because the objects in free fall. The acceleration due to gravity is 1.62 m/s^2 which is about 1/6 that of the acceleration due to gravity on earth.

How long will it take the lander to change velocity from 20 m/s to 0.5 m/s?
Time: V-Vº/a. Time = 20 - .5 / 1.62 ----> 19.5/1.62= 12.04 seconds to change from a velocity of 20 m/s to .5 m/s.

What is the thrust (T) of the engines?

So using the information can you help me find thrust?

• Physics THRUST -

a= (v₂²-v₁²)/2h =
=(0.5²-20²)/2•100= - 2 m/s²
F=m(a-g)= 20000•(2-1.62) =2.76•10⁴ N

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