Bowling ball force problem

nerak

I am having difficulty solving this problem. I even asked my teacher for help but her equation did not work and I am confused even more. Can someone please help me?

Q. When you lift a bowling ball with a force of 82 N, the ball accelerates upward with an acceleration a. If you lift with a force of 99 N, the ball's acceleration is 2*a.
a) Find the weight of the bowling ball.
b) Find the acceleration a.

This is how I tried it but i dont know if this is correct:

82N-w=m*a

99-W=2ma

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Claude Bile

Your equations look correct, however they appear to overcomplicate the problem. The question basically states that 17 N provides an upward acceleration of m*a.

Thus if 82 N provides an upward acceleration of m*a, (82-17)N must provide no acceleration - this is the weight of the ball.

Now you know both m*a and m*g, two equations with two variables that are relatively easy to solve.

Claude.

krab

Originally posted by Claude Bile
Your equations look correct, however they appear to overcomplicate the problem. The question basically states that 17 N provides an upward acceleration of m*a.
I find that to be a rather peculiar comment. Nerak, your equations are correct, AND they are the simplest description of the problem. Claude, the question does NOT "basically state that 17 N provides an upward acceleration of m*a". You got that be intuitively making exactly the subtraction suggested by Nerak's equations. Do not dissuade people from translating a probelm into equations. Intuition won't get you far in physics.

Claude Bile

Originally posted by krab
I find that to be a rather peculiar comment. Nerak, your equations are correct, AND they are the simplest description of the problem. Claude, the question does NOT "basically state that 17 N provides an upward acceleration of m*a". You got that be intuitively making exactly the subtraction suggested by Nerak's equations. Do not dissuade people from translating a probelm into equations. Intuition won't get you far in physics.
True, the question did not explicitly state that 17 N provides an upward acceleration of m*a, rather it is a logical derivation from the information provided in the question, there was no intuition involved.

I did not intentionally attempt to dissuade Nerek from using his (correct) equations, I merely offered a worded interpretation of how to arrive at the answer (as Nerek was unsure of whether he was correct) that I thought may be helpful.

Claude.

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