Solving a Lab w/ Friction: Need Help!

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    Friction Lab
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The discussion focuses on a lab experiment involving two masses on an incline to determine the coefficient of friction. The setup includes mass A being pulled by mass B, which falls, and the user is unsure how to calculate the force of friction after finding the system's acceleration. Initial calculations for the forces acting on the masses are presented, but the user has not included the friction force formula or the total mass in their analysis. Respondents encourage the user to apply Newton's second law (F = ma) and remind them to incorporate the necessary formulas for friction. The conversation emphasizes the importance of understanding the forces at play to solve the lab effectively.
fishfish
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Homework Statement



Hi, I'm new the PF and I was wondering if someone could help me with my lab.

physicsab-1.jpg


This was the basic set up of our lab, with one mass being pulled by another mass up an incline. The ramp was placed on a desk while mass B was left to fall towards the ground. What we were supposed to do was dertermine the coefficient of friction of the material ( coloured red ) under mass A for each different run that we did with different materials. I don't really know where to start on this lab, other than finding the acceleration of the system, but what I'm really troubled with is having to find the force of friction on the incline...

For the first run...

mass of block A= 0.185 kg
mass of block B = 0.143 kg
dots on tickertape= 84 dots
time ( estimated from tickertape) = 1.4s

Homework Equations



∑F= Fgy _ Fgx(paralell)
= mygy + mxgsinθ

The Attempt at a Solution



∑F= mygy + mxgsinθ
= (0.143kg)(9.8m/s2) + (0.185kg)(-9.8sin16°)
= 0.9 m/s2



And then after this I don't know where to go...
 
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fishy welcome to pf!

hi fishfish! fishy welcome to pf! :smile:
fishfish said:
∑F= mygy + mxgsinθ
= (0.143kg)(9.8m/s2) + (0.185kg)(-9.8sin16°)
= 0.9 m/s2

(i assume you're intending to use F = ma to find the acceleration)

you haven't included the formula for the friction force, nor the total mass :wink:
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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