What Was the Mass of the Original Stack of Books?

AI Thread Summary
The problem involves a stack of books on a frictionless surface, initially accelerating at 4 m/s² under a force F. When a 9 kg book is added, the acceleration decreases to 2.5 m/s² with the same force applied. To find the mass of the original stack, Newton's second law can be applied, where the force equals mass times acceleration. The discussion highlights confusion over how to start solving the problem due to a lack of information. Ultimately, the key to solving the problem lies in applying the relationship between force, mass, and acceleration.
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Homework Statement



A stack of books rests on a level frictionless surface. A force F acts on the stack, and it accelerates at 4 m/s2. A 9 kg book is then added to the stack. The same force is applied, and now the stack accelerates at 2.5 m/s2. What was the mass in kg of the original stack?


Homework Equations



KE = 1/2mv^2
W = FD


The Attempt at a Solution


I don't even know where to begin with this problem. Neither of the two equations is doable because I'm lacking necessary information, and that's all that's in the textbook except for Hooke's Law.
 
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