a. A skateboarder of mass 50kg is initially at rest on a level road. During a kick, the ground exerts a forward force of 150N on her while friction and air resistance together exert 40N backward. State the magnitude and direction of the net horizontal force acting on the skateboarder during the kick.
b. Describe the resulting change in her state of motion during this interval.
c. After 2s she stops kicking and only rolls. The opposing force of 40N backward still acts and no forward force is applied. State the direction of the net force acting on her now.
d. Explain in one sentence each: (a) what happens to her speed immediately after she stops kicking, and (b) what happens when the skateboard finally comes to rest and the net force becomes zero.