bowling ball 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

[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.