Final answer:
Newton's first law states that an object at rest or moving at a constant velocity will remain so unless acted upon by a net force, which applies to a car moving at constant velocity. When a person stands up or a car accelerates, they are applying forces to change their state, which involves (but is not limited to) overcoming static friction.
Step-by-step explanation:
In answering the question of whether one should keep their heel on the ground while braking, the context suggests a focus on driver's education, which while important, is not directly related to the Newton's laws examples provided. However, when evaluating the application of Newton's first law in different scenarios, we can summarize as follows:
Newton's First Law and Constant Velocity
Newton's first law states that an object will remain at rest or move at a constant velocity unless acted upon by a net external force. Thus, when your car moves at constant velocity down the street, Newton's first law does apply, as the car will continue to move in a straight line with constant speed unless a force is applied to change that state.
Application in Different Scenarios
Regarding the scenarios given:
- a person standing up from a seated position involves overcoming static friction and the force of gravity to change from a state of rest to a state of motion.
- a car accelerating while driving involves a net force being applied to change the car's velocity, which is an example of Newton's second law of motion.
Lastly, regarding the statement about static friction:
- Option a might be chosen if a body is not moving despite an applied force because the static friction has not been overcome.
- Option b could be chosen if a body starts sliding because the force applied has exceeded the maximum static friction.
- Option c is incorrect because if the applied force is less than the maximum static friction, the body will not move, contradicting the typical context of braking.