Newton's Three Laws of Motions:
Isaac Newton came up with three basic ideas that are applied to the physics of most motion. The ideas that he has developed have been tested and verified numerous times over the years and these ideas are now called Newton's Three Laws of Motions. The three laws are:
- The law of inertia
- F=ma
- For every action there is an equal and opposite re-action.
Newton's First Law of Motion:
According to Newton's first law "an object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force." We recognise this as Galileo's concept of inertia.
This means that an object at rest, will want to remain at rest, while objects in motion will want to remain at constant velocity. This means that objects have a tendency of doing what they're doing as all objects resist changes in their state of motion. In the absence of an unbalanced force, an object in motion will remain and maintain its state of motion. It is only until an external force is applied that the object will change its motion.
According to Newton's first law "an object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force." We recognise this as Galileo's concept of inertia.
This means that an object at rest, will want to remain at rest, while objects in motion will want to remain at constant velocity. This means that objects have a tendency of doing what they're doing as all objects resist changes in their state of motion. In the absence of an unbalanced force, an object in motion will remain and maintain its state of motion. It is only until an external force is applied that the object will change its motion.
An example of Newton's first law in every day life is that if you're travelling in a car and it is moving at a high speed and you come to a sudden stop, it is possible that you would be sent flying forward, this is because your body is trying to remain at the same velocity that it was going before. This is the reason why we have to wear seat belts, as if it wren't for the tension in the seatbelt, you would keep on moving while the car has stopped. The cause of your change in motion was the sudden brake on the car, which is the external force.
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Newton's Second Law of Motion:
Newton's second law is the most powerful out of the three as it allows quantitative calculations of dynamics such as "how do velocities change when forces are applied?". According to Newton's Second Law of Motion, a force only causes a change in velocity (acceleration). Newton's second law states "the rate of change of momentum is proportional to the imposed force and goes in the direction of the force." This means that when an unbalanced force acts on a body, the resulting force equals the mass times acceleration. This is summarised by saying F=ma (F - force, m - mass and a - acceleration).
Newton's second law is the most powerful out of the three as it allows quantitative calculations of dynamics such as "how do velocities change when forces are applied?". According to Newton's Second Law of Motion, a force only causes a change in velocity (acceleration). Newton's second law states "the rate of change of momentum is proportional to the imposed force and goes in the direction of the force." This means that when an unbalanced force acts on a body, the resulting force equals the mass times acceleration. This is summarised by saying F=ma (F - force, m - mass and a - acceleration).
An example of Newton's second law is that when the same force is applied to different objects it will have different velocities. This is because if you keep the force constant and change the mass, the acceleration will be different. For example, if you throw a small rock with a force of 20N, it would be moving at a fast speed. However, if you try and move a car with the same amount of force, its acceleration will decrease or go slower (decelerate) as its mass is heavier.
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Newton's Third Law of Motion:
Newton's third law of motion states "for every action there is an equal and opposite reaction." This means that for every force, there is an equal reaction force but in the opposite direction. It means that if an object pushes another object, it would get pushed back in the opposite direction but with the force that the object has pushed it, this is because forces are found in pairs. Acting forces encounter other forces in the opposite direction.
Newton's third law of motion states "for every action there is an equal and opposite reaction." This means that for every force, there is an equal reaction force but in the opposite direction. It means that if an object pushes another object, it would get pushed back in the opposite direction but with the force that the object has pushed it, this is because forces are found in pairs. Acting forces encounter other forces in the opposite direction.
For example, shooting a cannonball. When a cannonball is fired through the air, through the act of explosion, the cannon is pushed backwards. The force that pushes the cannonball forwards is equal to the force that pushes the cannon back, however, the effect on the cannon isn't as visible as the effect on the cannonball as the cannon has a larger mass.
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