Question

A child is pulling a wagon across the grass but friction between the grass and wheel creates a force in the opposite direction . If the wagon is speeding up , what does that mean about the two forces ?

Answer 1

ANSWER

The applied force is larger than the frictional force

EXPLANATION

If we draw a free-body diagram,

By Newton's second law, for the horizontal forces is,

$F_a-F_f=m\cdot a$

If the wagon is speeding up, it means that there is a positive acceleration. Therefore, the difference Fa - Ff is positive,

$\begin{gathered} F_a-F_f>0 \\ \text{therefore} \\ F_a>F_f \end{gathered}$

Hence, the applied force is greater than the frictional force.