Question

directions: each one of newtons laws can play a role in any one particular situation. however, one of the laws is often most obviously dominant in governing the motion of a situation. pick which of newtons laws most governs the situations described below. explain your answers in the space below, just be sure to number the explanation.
a. first law b. second law c. third law

1. a helicopter must have two sets of blades in order to fly with stability.
2. you usually jerk a paper towel from a roll in order to tear it instead of pulling it smoothly.
3. a student desk changes the amount of force it puts on other objects throughout a school day.
4. heavy objects are not easier to move around in a horizontal fashion on the moon than on the earth.
5. the stronger, heavier team in a tug - of - war does not create a larger tension in the rope than the weaker, lighter team.

Explanation:

Question 9:

A helicopter's main rotor creates a downward force on air, and by Newton's Third Law, air pushes up (lift). But this also creates a torque that would spin the helicopter body. A tail rotor (second set) applies a force, and via Third Law, the reaction force counteracts the torque. So the dominant law is the Third Law (action - reaction pairs) for the force interactions that allow stable flight.

When you jerk the paper towel, the roll tends to stay at rest (inertia, Newton's First Law: an object at rest stays at rest unless a net force acts on it). The quick jerk means the force on the towel is applied for a short time, and the roll doesn't have enough time to start moving with the towel, so the towel tears.

A student desk exerts a normal force on objects (like books) equal to the weight of the objects (Newton's Third Law: the desk and the object exert equal and opposite forces on each other). As objects are added or removed, the weight (and thus the force the desk exerts) changes. So the interaction is governed by the Third Law (action - reaction between desk and objects).

Answer:

c. Third Law

Question 10: