Answer:

Explanation:
The attached figure shows the whole description. Considering the applied force is 100 N.
The acceleration of both blocks A and B, 
Firstly calculating the mass m using the second law of motion as :
F = ma
m is the mass


m = 125 kg
It suddenly encounters a surface that supplies 25.0 N a friction, F' = 25 N



So, the new acceleration of the block is
. Hence, this is the required solution.
The standard states of elements are the forms that they adopt at a temperature of 25°C and pressure of 1 atmosphere. These forms of the elements are the reactants in the formation equations of multi-element substances. The heat of formation (∆Hf°) of an element in its standard state is zero
The net force on an object subject to friction is equal to the sum of the applied force and the frictional force.
Mathematically,

Here, m is mass of object and a is its acceleration. We take frictional force negative because it opposes the motion of object.
Given,
,
and 
Substituting these values in above formula, we get
.
Thus, the acceleration of an object is 
True! In order for work to be done, a force must cause movement.