Question

A window washer pulls herself upward using the bucket-pulley apparatus. The mass of the person plus the bucket is 65 kg.
(a) How hard must she pull downward to raise herself slowly at constant speed?
(b) If she increases this force by 10%, what will her acceleration be?

Answer 1

a)
To go up at constant velocity, the net force on her should be 0. The force upwards must equal the total weight.
W = mg
= 9.81 x 65
= 637.65 N
Therefore, she must exert a force of 637.65 N to move upwards at constant velocity

b) Net force = 1.1F - W(1.1 represents 10% increase)
We know from the previous part that F = W
1.1W - W
= 0.1W
Net force = 63.8 N
Using Newton's second law of motion:
F = ma
a = F/m
a = 63.8/65
= 0.98 m/s²