Final answer:
To accelerate forward when walking, one applies Newton's third law, where the force exerted backward on the ground results in a forward reaction force from the ground, overcoming friction and enabling forward motion.
Step-by-step explanation:
When you begin to walk forward, the force that allows you to accelerate is a result of Newton's third law of motion. As you push backward on the ground with your foot, the ground pushes forward on you with an equal and opposite reaction force. This is similar to how a professor pushes a cart: When a professor exerts a backward force on the ground with their foot (Ffoot of 150 N), the ground exerts a forward reaction force (Ffloor of 150 N) on the system comprising the professor, cart, and equipment. This forward reaction force is what accelerates the system forward. Additionally, friction opposes the motion, but as long as the force exerted by the person is greater than the friction, the person or system will move forward.