Newton's Third law problem Astronaut and Force

AI Thread Summary
An 81.0 kg astronaut exerts a force of 794 N on his chair while at rest, calculated using the weight formula W = m*g. When accelerating upwards at 18.0 m/s², the astronaut's net force equation combines weight and chair force, leading to Fnet = w + Fchair. The astronaut's weight is 794 N, and the net force during acceleration is calculated as 81 kg * 18 m/s², resulting in a total force of 1458 N. The correct force exerted on the chair is found by rearranging the equation, leading to an answer of 664 N, but the error lies in not properly accounting for the direction of forces. Properly considering the signs of forces is crucial for accurate calculations.
sweetheart901
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The question states:

How much force does an 81.0 kg astronaut exert on his chair while sitting at rest on the launch pad?

the answer that I got was 794 N
using...
W=m*g and
Fnet=w+fchair=0

But I cannot seem to get the right answer for this second question:

How much force does the astronaut exert on his chair while accelerating straight up at 18.0 m/s^2?


I know that Fnet= w+ Fchair
and also Fnet= m*a
so 81 kg * 18m/s^2= 794 + Fchair
the answer I get for Fchair is 664 but its not the correct answer.
what am I doing wrong??
 
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Recall forces have directions associated with them, and thus signs. Be careful with your signs.
 
Thank you! I guess that was my fault for making a silly error >.<
 

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