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# Physics Help Please watch

1. Last question of homework, really don't understand it.

''An astronaut of mass 80kg stand on the horizontal floor of a spaceship moving vertically with acceleration a. If the acceleration due to gravity on the astronaut is g= 9.8 ms^-2, write a mathematical expression for and calculate the value of the reaction force R between the astronaut and the floor of the spaceship when:

1, a = 0;
2, a = 8 ms^2 upwards;
3, a = 8 ms^2 downwards.

Would be a real great help if someone could tell me what to do!
2. This one needs to be in the physics section to get the best chance of replies.
However, as I'm here!
The key equation is F=ma where F is the resultant force acting on the astronaut.
The resultant force in each case will be the sum (or difference*) of the two forces we have here
his weight (mg) and
the reaction of the floor pushing up on him, R
The weight acts downwards and the reaction upwards so if one is positive the other is negative.
*If we let upwards be positive then the resultant force is always R-mg

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