Suppose two children push horizontally, but in exactly opposite directions, on a third child in a wagon. The first child exerts a force of 75.0 N, the second a force of 95.0 N, friction is 12.0 N, and the mass of the third child plus wagon is 21.0 kg.

(c) Calculate the acceleration.
m/s2
(d) What would the acceleration be if friction is 20.0 N?

Value of acceleration in each case is  

Explanation:

According to newton's law :

      ...equation 1.

In the given case, Force by both the children - Friction force .

Putting value of F in equation 1.

Now, if friction force = 20 N.

Therefore,

Putting value of F and a in equation 1.

Hence , this is the required solution.

positive reinforcement? ?

i am pretty sure it is c because when people are closer together, they cannot move as freely. picture being in a mostly full elevator, for instance. the people are right next to you, and you can barely move.