Newton's Law of Motion - First, Second & Third - Physics
The Organic Chemistry Tutor
Newton's Laws of Motion
In this article, we will discuss Newton's laws of motion. There are three laws that we will cover, starting with the first law.
Newton's First Law
The first law states that an object at rest will remain at rest unless acted upon by an unbalanced force. For example, if a box is resting on a surface and no force is applied, the box will not move as the weight force of the box is balanced by the normal force of the ground. However, if an unbalanced force is applied, the box may begin to move.
Newton's Second Law
The second law states that an object in motion will continue in motion unless acted upon by a net force. For instance, if a ball is rolled on a rough surface, it will eventually come to rest due to friction. However, if the ball is rolled on a smooth surface, it will continue to move for a longer time as there is less friction. In outer space, where there is virtually no friction, an object in motion can continue in motion for an extended period of time.
In terms of problem-solving, there are a few things to keep in mind. If an object is at rest, then the force acting on it is equal to zero. If an object is moving at a constant velocity, then the net force acting on it is also equal to zero. The acceleration is defined as the change in velocity over time and is proportional to the net force acting on an object.
If the mass of an object is increased while keeping the acceleration constant, the net force acting on it will increase. Similarly, if the magnitude of the acceleration is increased while keeping the mass constant, the net force acting on it will also increase. If the net force acting on an object is constant, then the relationship between mass and acceleration is inverse.
Newton's Second Law of Motion
If you quadruple the mass and triple the acceleration, the force will increase by a factor of 12. This is basically what Newton's second law of motion states, which is that the net force is equal to the mass times the acceleration. Another way to express this law is through the equation F = ma, where F is the net force, m is the mass, and a is the acceleration.
Momentum and Impulse
Momentum, represented by the symbol p, is the product of an object's mass and velocity. Newton's second law can also be expressed as the net force being equal to the rate of change of momentum with respect to time. This leads to the impulse-momentum theorem, which states that impulse (the product of force and time) is equal to the change in momentum.
Newton's Third Law of Motion
Newton's third law states that for every action, there is an equal and opposite reaction. This means that if you apply a force on an object, there will be a reaction force applied to you that has the same magnitude but opposite direction.
Examples
- Throwing a basketball: If a person jumps in the air and throws a basketball, there will be a recoil force applied to the person due to Newton's third law. The ball will travel further than the person because it has less mass and will therefore experience a greater acceleration.
- Throwing a ball in the ocean: If you throw a ball while in a boat in the ocean, the boat will move slightly in the opposite direction due to the reaction force. However, because the combined mass of you and the boat is much larger than the ball, the distance that the boat moves is insignificant.
- Throwing a ball in space: If you're an astronaut in space and want to get back to Earth, you should throw the ball towards the moon so that the reaction force pushes you towards Earth.
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