Answer:
Explanation:
Given
Force by first child is [tex]F_1=75 N[/tex]
Force by second child [tex]F_2=90 N[/tex]
mass of third child and cart is 29 kg
If sufficient force is provided then system tends to change its current state i.e. starts moving
Net Force on system[tex]=F_2-F_1-f_r=90-75-12=3 N[/tex]
net acceleration[tex]=\frac{F}{m}=\frac{3}{29}=0.103 m/s^2[/tex]
If friction force is 15 N then the system would have been in rest as [tex]F_{net}=0[/tex]