Problem 4A: A car starts from rest (0 velocity) and begins moving forward. Thus

Question

Problem 4A: A car starts from rest (0 velocity) and begins moving forward. Thus Newton's first law applies: A body (car) at rest (0 initial velocity) remains at rest, unless acted upon by a net force. Since a car that begin moving is no longer at rest, according to Law 1 there must have been a net force on the car. Where does the net force that is pushing the car forward coming from? Discuss your answer in detail.

Problem 4B. The teacher who weighs 175 lbs. is standing on the floor and is not moving. If the teacher is not moving then in terms of Law 1 there must be no net force acting on the teacher. This no net force can be understood in terms of Law 3, the floor will push upward with a force of 175 lbs. which is exactly equal to the force the teacher's weight pushes downward on the floor due to gravity. If the teacher ate a LOT such that he weighed much more, say 300 lbs., and stood in exactly the same spot, the floor would push upward with a greater force of 300 lbs. to counter balance the force of gravity downward due to the heavier weight. How is the floor so smart as to always push upward with the right force to counter the downward force of gravity? Discuss your answer in detail.

Explanation / Answer

4A. THe force that moves the car comes from the engine of the car or the car can be pushed by a group of people or it can e pulled by another vehicle. the only point to address here is that the movement of a body at rest can happen if and only if it is acted upon by some force.

4B. According to Newtons third law, to every action there is equal and opposite reaction.

Here the reaction force is given by the floor.

The floor building is constructed in such a way that it can withstand a compressive load which lies inside the safety limit. once the load exceeds the safety limit the building collapses which means that the downward force on the floor is greater than the reaction force the floor can provide. so the point here is that the balance of forces makes the objects in equilibrium position.

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