Solving Physics: Chris the Inventive - Acceleration & Force

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Chris is trying to retrieve an apple from a tree using a pulley system, pulling with a force of 272.5 N while weighing 464 N himself, with the chair weighing 67 N. The acceleration of the system has been calculated correctly as approximately 0.258 m/s². However, there is confusion regarding the calculation of the force Chris exerts on the chair, specifically whether to include the mass of both Chris and the chair in the force equation. The net force acting on the chair must account for both the weight of Chris and the chair, leading to the correct application of F = m(a + g). Accurate calculations are essential for determining the force exerted in this scenario.
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An inventive child named Chris wants to reach
an apple in a tree without climbing the tree.
Sitting in a chair connected to a rope that
passes over a frictionless pulley, Chris pulls
on the loose end of the rope with such a force
that the spring scale reads 272.5 N. Chris’s
true weight is 464 N, and the chair weighs
67 N.
The acceleration of gravity is g = 9.8 m/s2 .
A. Find the magnitude of the acceleration of
the system.
Answer in units of m/s2.

B.
Find the magnitude of the force Chris exerts
on the chair.
Answer in units of N.



i got the acelleration and it was marked correct (0.258380414312617702)

but when i look for the force which i used f=ma... it was marked wrong... i tried first in N than in kg and still nothing...
 
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Chair is going up with an acceleration a. Weight of Chris acts in down ward direction. So net reaction on the chair is F = m(a+g)
 
ok would i use the mass of the chair only or include the kids too?
 

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