The mechanical advantage of the pulley is 3.56
Explanation:
The Mechanical Advantage (MA) of a pulley system is given by

where
Load is the weight of the object lifted
Effort is the force applied in input
For the pulley in this problem, we have:
Effort = 55 N
While the load is the weight of the box of mass m = 20.0 kg:

Substittuing, we find the MA of the pulley:

#LearnwithBrainly
Acceleration =(v-u)/t
Put in values And re arrange gives initial velocity of -2 m/s
Explanation:
The work done equals the change in energy.
W = ΔKE
W = 0 − ½mv²
W = -½ (0.270 kg) (-7.50 m/s)²
W = -7.59 J
Work is force times displacement.
W = Fd
-7.59 J = F (-0.150 m)
F = 50.6 N
the answer is J. 3,900,000 got it right on the test