Newton’s Laws of Motion The Three Laws of Motion

Newton’s 1st Law of Motion Newton’s first law states that every object continues in a state of rest, or of uniform speed in a straight line, unless acted on by a nonzero net force.

“An object in motion tends to stay in motion and an object at rest tends to stay at rest.”

http://www. youtube. com/watch. v=d7iYZPp2zYY http://www. youtube http://www.youtube.com/watch?v=d7iYZPp2zYY http://www.youtube.com/watch?v=eIHv5FdKet0

Newton’s 2nd Law of Motion Newton’s second law states that the acceleration produced by a net force on an object is directly proportional to the magnitude of the net force, is in the same direction as the net force, and is inversely proportional to the mass of the object. F = ma force = mass x acceleration

http://www.military.com/video/rockets/aircraft-rockets/human-g-force-testing-at-1000kmh/663113048001/

Newton’s 3rd Law of Motion Newton’s third law states that whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object.

https://www.youtube.com/watch?v=Mine_SY4PNw

What does all three of Newton’s Law have in common?

Different forces Contact Forces Action-at-a-distance forces Frictional Force Gravitational Force Tension Electrical Normal Magnetic Air Resistance Applied Spring For this unit, we will only be dealing with contact forces.

What is a force? A force is a push or pull acting upon an object as a result of its interaction with another object.

Gravity, g The first force we will investigate is that due to gravity, and we'll call it the gravitational force. We know that the acceleration due to gravity (if on Earth) is approximately g = 9.8m/s2. Vertically: The force (weight), by Newton's Second Law is F = m g

Normal, FN The normal force one which prevents objects from 'falling' into whatever it is sitting upon. It is always perpendicular to the surface with which an object is in contact. For example, if there is a crate on the floor, then we say that the crate experiences a normal force by the floor; and because of this force, the crate does not fall into the floor. The normal force on the crate points upward, perpendicular to the floor and equal to the weight.

Friction, Ff Related to the normal force is the frictional force. The two are related because they are both due to the surface in contact with the body. Whereas the normal force was perpendicular to the surface, the frictional force is parallel. Furthermore, friction opposes motion, and so its vector always points away from the direction of movement.

Push and Pull Another force which may act on an object could be any physical push or pull. This could be caused by a person pushing a crate on the floor, a child pulling on a wagon, or in the case of our example, the wind pushing on the ship.

Tension Tension in an object results if pulling force act on its ends, such as in a rope used to pull a boulder. If no forces are acting on the rope, say, except at its ends, and the rope itself is in equilibrium, then the tension is the same throughout the rope.

Representations

http://www.youtube.com/watch?v=8vOVq_9yHS0

Free-Body Diagram What is a free-body diagram? A free-body diagram is a sketch of an object of interest with all the surrounding objects stripped away and all of the forces acting on the body shown.

Free-Body Diagram

How to draw a FBD Draw the picture of the entire system. ID the system Draw the system alone Draw and label the force vectors on the system

Step #2 Static crate on an incline. (no motion) FN = F (Force perpendicular to the incline) FF (Friction Force parallel To the incline) T F// (Force parallel To the incline) Weight (mg) Step #1 Step #2 Static crate on an incline. (no motion)

Step #2 Static crate on an incline connected to a hanging crate Step #2 Static crate on an incline connected to a hanging crate. (no motion) FN T T Fll W2 T W1 W

Net Force Net force is the sum of the forces in a system. To calculate for the net force on a system, add all the forces that are going in the same or opposite direction.

25000 N 20000 N 2000 N 14000 N Total force horizontally = 20000 – 2000 = 18000 N Total force vertically = 25000 – 14000 = 11000 N

F Normal Ffriction F = ma Weight

F Normal Weight

Equilibrium When objects are moving at a constant velocity, the object is in dynamic equilibrium (all the forces on the object balance) When objects are not moving, the object is in static equilibrium (all the forces on the object balance).

Dynamics When objects move with varying speed (acceleration), the object is not in equilibrium. There is an imbalance in the forces acting on the object.

Newton’s 1st Law indepth Who is Newton? Isaac Newton (January 4, 1643 to March 31, 1727) was a physicist and mathematician who developed the principles of modern physics, including the laws of motion, and is credited as one of the great minds of the 17th century Scientific Revolution. In 1687, he published his most acclaimed work, Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), which has been called the single most influential book on physics. In 1705, he was knighted by Queen Anne of England, making him Sir Isaac Newton. https://www.biography.com/people/isaac-newton-9422656

How the Law of Inertia came to be.