Answer:
, in the direction of F2
Explanation:
The magnitude of F2 is larger than that of F1: this means that the wagon will tend to move in the direction of F2. Therefore, the direction of friction will be opposite to the direction of motion, therefore in the direction of F1.
Let's now take the direction of the force exerted by the second child, F2, as positive direction. Then the direction of F1 and of the force of friction () will be negative: so we have
We can write the equation of the forces for the third child+wagon:
where
m = 30.0 kg is the combined mass of the child + the wagon
Now we can solve the equation for a, to find the acceleration: