Above is my data for friction lab and I\'m not sure if I did correctly to determ

Question

Above is my data for friction lab and I'm not sure if I did correctly to determine the value of F1/Fn1 and F2/Fn2.

My answers are:

F1/Fn1=0.5/(0.2*9.8)= 0.255

F2/Fn2= 0.2/(0.5*9.8)= 0.041

And also I need more information to answer questions below.

Q1, How do the experimentally determined ratios of the applied and normal forces compare between cup types? What does the ratio of the applied force and the normal force represent?

Q2, Look carefully at the force applied right before the cups begin to slide and compare with the force applied as the cup is sliding at constant velocity. Is there a difference in the magnitude of forces? If so, explain. What can you conclude about the coefficients of friction (?s and ?k) using the equation Ff=?FN?

Thanks for the help!!!

Explanation / Answer

Friction coefficient = F/Fn = F/(mass * 9.8)

F1/Fn1 = 0.5/(0.3 * 9.8) = 0.17

F2/Fn2 = 0.2/(0.15 * 9.8) = 0.14

Q1.) The greater the ratio of the applied and normal force greater is the friction between the cup and the surface.

The ratio of the applied and the normal force represent the friction coefficient between the cup and the surface below.

Q2.) The force applied just before the cup began to slide was GREATER than afte the cup begins to slide.

The coefficient of friction before the cup starts sliding is the STATIC FRICTION (?s) and after it starts sliding is KINETIC FRICTION (?k)

Before sliding :   Ff = ?sFN

After sliding begins: Ff=?kFN

Now, Force applied before sliding >  Force applied after sliding begins

---> ?sFN > ?kFN

----> ?s > ?k

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