Stupid physics problem.

[Adam Y.]

Originally Posted by UsmanB

i did a quick search of ur problem on google and found this problem on a forum:

A window washer pulls herself upward using the bucket-pulley apparatus show in Fig. 4-42 (the woman is in a bucket, a rope tied to the top of the bucket, and she's pulling on the downward direction of rope that goes up over the pulley) (a) How hard must she pull downward to raise herself slowy at a constant speed? (b) If she increases this force by 10 percent, what will her acceleration be? The mass of the person plus the bucket is 65 kg.

This was the reply from a member.

Find the accelerations of all four parts. (g=10)

a = [(m2-m1)/(m1+m2)]g

a1 = [(180kg - 120kg)/(180kg + 120kg)]10m/s^2
a1 = 2m/s^2

a2 = [(120kg - 80kg)/(120kg + 80kg)]10m/s^2
a2 = 2m/s^2

a3 = [(80kg - 40kg)/(80kg + 40kg)]10m/s^2
a3 = 3.33m/s^2

a4 = [(40kg - 0kg)/(40kg + 0kg)]10m/s^2
a4 = 10m/s^2


Find the time in seconds.

s = .5at^2

16m = .5 (2m/s^2) t^2
t^2 = 16m
t1 = 4s

t2 = 4s (same acceleration)

16 = .5 (3.33m/s^2) t^2
t3 = 3.1s

16 = .5 (10m/s^2) t^2
16 = 5t^2
t^2 = 3.2
t4 = 1.8s

Adding the times of 4+4+3.1+1.8 = 12.9 seconds.

Acckkk..... You just gave me the answer to the problem above that post. Nice try but wrong problem.

good luck and im sure that if u looked in the chapter ur doing right now u could find perhaps an example, i know the physics book i have right now doesnt have each example for each type of problem so u have to play with equations given.

I did play with the equations. The only problem is that if Im getting the wrong answer for one part I should be getting wrong answers both parts. It's double jeporday. Get one part worng and get all the other parts wrong. Friction=Mu*FN. Well how do I get the right answer when my force of friction is wrong.