Given that the masses are m1 = 5.60 Kg and m2 = 11.20 Kg
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Apply Newtons law for the mass m2 then
m2g - T = m2a
for the mass m1
T - m1g = m1a
From the above two equations we get
m2g - m2a - m1g = m1a
a = (m2g - m1g) / (m1+m2)
= ---------- m/s2
if the acclearation reduced to 50% then the new accelaration is a1 = a/2
If we exert a force f on the mass m1 then the situation is as shown in figure
Apply Newtons law for the mass m2 then
m2g - T = m2*a1
for the mass m1
T - m1g - f = m1*a1
From the above two equations we get
m2g - m2*a1 - m1g - f = m1*a1
f = m2g - m2*a1 - m1g - m1*a1
then we get the applied force f = ----------- N