Zusammenfassung der Ressource
Newton's Laws of Motion
- 1st Law
- Newton's first law of motion states that a body will remain in its state of rest or uniform
motion in a straight line unless acted upon by a resultant force.
- Also called the Law of Inertia
- Inertia is the resistance of all bodies to change in
their initial state of rest or uniform velocity.
- Mass is a measure of Inertia
- An object with a larger mass has a more Inertia.
- When you kick a bowling ball and a tennis ball with the same
force, the tennis ball will move much more than the bowling ball.
- Because the bowling ball has a greater mass and more inertia.
- Meaning that once an object moves, it will keep moving in a straight line.
- But this doesn't happen in our daily lives
because friction causes objects to stop moving.
- Friction is the resultant force.
- If you continuously push the object to keep it moving, the
force you apply on the object is also a resultant force.
- A body moving with constant velocity
experiences zero net/resultant force.
- 2nd Law
- Newton's second Law of Motion states that the rate of change of momentum is proportional to the
resultant force acting on it and acts in the direction of the resultant force.
- Momentum: mass x velocity
- Note: both the mass and velocity can change! Not everything has constant mass.
- For a body with constant mass, F=m x difference in velocity/ time=mass x acceleration.
F=ma
- When F=ma is used in the context of a free falling object, you will get its weight, W=mg.
- When resultant force is zero, there is no acceleration.
- This compliments Newton's first Law of motion!
- 3rd Law
- Newton's third Law of Motion states that is Body A exerts a force on Body B, Body
B will exert an equal and opposite force on Body A.
- The forces exerted by both Body A and B are termed as action-reaction pairs.
- Action-reaction pairs are 2 forces (same type of force) acting in opposite directions from each other.
- The forces could be acting at a distance away from each other.
- Or they could be contact forces.
- Force exerted by a book on a table and force exerted
by the table on the book.
- Eg. Gravitational force of attraction exerted by Moon on Earth and the gravitational
force of attraction exerted by the Earth on the Moon.
- Magnetic forces of repulsion between like poles of a magnet.
- The action and reaction forces do not act on the same body, so they do
not balance to produce zero resultant fore on a single body.