Newton’s Laws of Motion Newton’s Laws and Bernoulli’s Principle Newton’s Laws of Motion

Newton’s Three Laws of Motion Newton’s Laws and Bernoulli’s Principle Newton’s Three Laws of Motion Sir Isaac Newton first presented his three laws of motion in the Principia Mathematica Philosophiae Naturalis in 1686. To understand Newton’s laws of motion, you must remember that on Earth we always have GRAVITY pulling down on us and AIR around us. Newton’s laws are used in the design of aircraft and spacecraft.

Newton’s Laws and Bernoulli’s Principle First Law of Motion Objects in motion tend to stay in motion AND Objects at rest tend to stay at rest UNLESS Something pushes or pulls on the object. Newton’s First Law: In simple terms, Newton’s First Law states that “objects in motion tend to stay in motion and objects at rest tend to stay at rest.” That is, something must happen in order for an object to start moving. Consider a blackboard eraser sitting still, or “at rest,” on a table. In order to make the eraser move, we must push on it. Otherwise the eraser will stay at rest. Newton observed that an external force was required to change the state of an object from rest to motion or from motion to rest. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

Newton’s Laws and Bernoulli’s Principle First Law of Motion Example Think of a block sitting still, or “at rest”. If the block is to move, it must receive a push. Otherwise it will stay at rest. Push

Newton’s Laws and Bernoulli’s Principle According to Newton’s First Law, When Will the Block Stop? Push Push Push Push Push

Newton’s Laws and Bernoulli’s Principle First Law of Motion Example Think of a baseball thrown in space. Without GRAVITY to pull it down, the ball would just keep moving until something got in its way and stopped it.

Aerospace Examples of the First Law of Motion Newton’s Laws and Bernoulli’s Principle Aerospace Examples of the First Law of Motion The movement of an airplane changes when the pilot changes the throttle setting (or force) of the engine. More force moves the airplane at a greater speed.

Aerospace Examples of the First Law of Motion Newton’s Laws and Bernoulli’s Principle Aerospace Examples of the First Law of Motion The movement of a model rocket being launched into the atmosphere The rocket was at rest (not moving) until the force of the engine pushed it upward.

Newton’s Laws and Bernoulli’s Principle Second Law of Motion The acceleration of an object depends on: The size of the force on the object The direction of the force on the object The mass of the object The relationship: F = m * a Force = mass * acceleration Or a=F/m acceleration = Force/mass With his second law, Newton quantified how externally applied forces affect the motion of objects. Mathematically, the statement of the second law of motion is below: The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector. In other words, we say that the sum of external forces acting on an object is equal to the mass of the object times its acceleration.

Examples of Second Law of Motion Newton’s Laws and Bernoulli’s Principle Examples of Second Law of Motion The direction of acceleration is the same as the direction of the external force. Remember the box? If you want to move the box to the right, you push toward the right. So there are two things we need to observe from this second law. First, the direction of the acceleration is the same as the direction of the external force. In other words, if you want to move the box to the right, you push to the right, and if you want to move the box to the left, you push toward the left. This seems obvious, but it is important to remember. Second, the magnitude of the acceleration is equal to the external force divided by the mass of the object. The bigger the object (the more mass), the smaller the magnitude of the acceleration given the same external force. In other words, if you push with the same force on a box and a car, the box will accelerate much faster than the car. Push Push If you want to move the box to the left, you push toward the left.

Examples of Second Law of Motion Newton’s Laws and Bernoulli’s Principle Examples of Second Law of Motion The bigger the object (the more mass), the more force is needed to accelerate the object. The magnitude (size) of the acceleration is equal to the external force divided by the mass of the object. Back to the box (but let’s add a car). 50 lb If you push the car and the eraser with the same force, Second, the magnitude of the acceleration is equal to the external force divided by the mass of the object. The bigger the object (the more mass), the smaller the magnitude of the acceleration given the same external force. In other words, if you push with the same force on a box and a car, the box will accelerate much faster than the car. The eraser will accelerate much faster than the car. 50 lbs 50 lbs

Newton’s Laws and Bernoulli’s Principle Third Law of Motion For every action, there is an equal and opposite reaction. You, on roller blades, push against a wall. Object A: You Object B: Wall Action: You apply a force on the wall. Newton’s third law is simply stated as the law of equal and opposite reaction. To interpret this law, we need to consider two different objects interacting with each other. We will complete some activities that will allow us to observe this law, but first, let’s change the mathematical expression above by using the second law in conjunction with the third. Reaction: The wall applies the same force back on you.

Examples of the Third Law of Motion Newton’s Laws and Bernoulli’s Principle Examples of the Third Law of Motion You, on roller blades, push against a wall. Object A: You Object B: Wall Your backward movement is the result of the wall pushing back against you.

Examples of the Third Law of Motion Newton’s Laws and Bernoulli’s Principle Examples of the Third Law of Motion Flaming hot gases are pushed out the bottom of a rocket. Reaction: The rocket moves upward Object B: Rocket Object A: Flaming hot gas Action: Gas is pushed downward out of the rocket

Third Law of Motion Examples Newton’s Laws and Bernoulli’s Principle Third Law of Motion Examples The upward movement of the rocket is the result of the gases pushing downward from the rocket.

Third Law of Motion Key Points Newton’s Laws and Bernoulli’s Principle Third Law of Motion Key Points The third law can be used to explain how a wing produces lift and a jet engine produces thrust. On a wing, the air is pushed downward because of the wing’s unique shape (an airfoil). In reaction, the air pushes the wing upward. http://www.grc.nasa.gov/WWW/K-12/airplane/newton3.html A jet engine produces hot exhaust gases which flow out the back of the engine. In reaction, a thrusting force is produced in the opposite direction.

Newton’s Laws and Bernoulli’s Principle Image Resources Microsoft, Inc. (2009). Clip art. Retrieved June 16, 2009, from http://office.microsoft.com/en-us/clipart/default.aspx National Aeronautics and Space Administration (NASA). (n.d.). Newton’s third law of motion. Retrieved June 19, 2009, from http://www.grc.nasa.gov/WWW/K-12/airplane/newton3.html