This diagram shows about question 3 in this diagram, the forces on the runner and on the ground are equal. why does the runner move forwards, yet the ground apparently does not move backwards?

According to newton's third law: every action has an equal and opposite reaction, so yes the ground does move backwards. You have 4 forces acting on you at any given time: pushing force, friction force, gravity, and normal force. you push against something to propel forward, you have to overcome gravity and friction, and normal force keeps things upright to prevent them from falling into each other. 

If everything is motionless at every instant, and time is entirely composed of instants, then motion is impossible, so it must be an illusion.


if you really want things to get confusing you can read up on zeno's dichotomy paradox stating that there is infinate amount of times you can divide something such as a distance traveled over time and you will stil 

Ithink the answer would be 1,350!