1. Newton's First Law of Motion
Three fundamental principles, called Newton's First, Second and Third Laws, form the basis of classical, or Newtonian, mechanics and have proved valid for all mechanical problems not involving speeds comparable with the speed of light and not involving atomic or subatomic particles. Newton's First Law states that a particle not subjected to external forces remains at rest or moves with constant speed in a straight line. This is also known as the Law of Inertia.
Newton's first law of motion is often stated as: An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
2. Newton's Second Law of Motion
The second law is the one that tells you how to calculate the value of a force. Force (measured in Newtons) is one of the fundamental physical properties of a system and comes in many forms. You might feel it as a push or pull (a mechanical force), while it is the value of your weight (the gravitational force of the Earth pulling on you) and can be seen in the repulsion or attraction of magnets or electric charges (electromagnetic force).
The Law is often stated as: The acceleration of a particle is directly proportional to the resultant external force acting on the particle and is inversely proportional to the mass of the particle, or a = F/m.
3. Newton's Third Law of Motion
If two particles (or bodies) interact, the force exerted by the first particle on the second particle (called the action force) is equal in magnitude and opposite in direction to the force exerted by the second particle (called the reaction force).
Suppose you are watching the lift off of a rocket, like the ones by SpaceX. You hear a deafening roar and see burning gases shooting from the exhaust vents of the rockets. At that moment, the rocket moves slowly upward. You can infer that the force for the lift off comes from the burning gases pushing against the shuttle rockets. Why does the shuttle system move in the opposite direction of the gases?
The forces on the rocket are similar to the forces in a collision between two tennis balls. When the balls collide, they are propelled in opposite directions. The rockets force burning gases downward through the exhaust vents. In response to these downward forces, the shuttle system moves upward. The motion of the rocket demonstrates Newton's third law of motion. When one object exerts a force upon a second object, the second object exerts an equal and opposite force upon the first object.
The third law of motion states that every action has an equal and opposite reaction. You can see equal and opposite forces interact when you blow up a balloon and release it, it moves in the opposite direction. The force propelling the balloon is equal and opposite to the force of the air leaving the balloon.
4. Newton's Law of Universal Gravitation
Newton's Law of Universal Gravitation states that a particle attracts every other particle in the universe using a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.
5. Einstein's Special Theory of Relativity
Einstein's theory about the relationship between space and time is based on two postulates: (1) that the laws of physics are invariant in all inertial systems and (2) that the speed of light in a vacuum is the same for all observers, regardless of the motion of the light source.
6. Zeroth Law of Thermodynamics
The principle states that if two bodies are each in thermal equilibrium with a third body, then the first two bodies are in thermal equilibrium with each other.
7. First Law of Thermodynamics
The First Law of Thermodynamics states that heat is a form of energy, and thermodynamic processes are therefore subject to the principle of conservation of energy. This means that heat energy cannot be created or destroyed. It can, however, be transferred from one location to another and converted to and from other forms of energy.
An astronomer discovers a planet with two moons. One moon is 2 times as far from the center of the planet as the other and 3 times the mass of the other moon. What is the ratio of the gravitational force on the first moon to the gravitational force on the second moon?
A 1-newton force and a 4-newton force act in opposite directions. What is the magnitude of the resultant force, in newtons?
An object starts from rest and accelerates at 6.0 m/s^2 for 4.0 seconds. How far does it travel?
(A) 8.0 m
(B) 12 m
(C) 48 m
(D) 96 m
(E) 288 m
Force A and Force B act on an object. Let theta equal the angle between the directions of the two forces. At what value of theta is the resultant force the greatest?
(A) 0 deg
(B) 45 deg
(C) 60 deg
(D) 90 deg
(E) 180 deg
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