TEKS 4B : investigate and describe applications of Newton’s laws such as in vehicle restrains, sports activities, geological processes and satellite orbits.

Demo 1 Crash Cart & Rubber Stopper

Teacher instructions 1.Obtain Crash cart (from Physics teacher) and a rubber stopper (from Chemistry teacher) 2.Put rubber stopper on back of cart. Push into a wall and have students observer what happens to the stopper (it will continue to move and fall into the cart) 3.Repeat above but secure the stopper to the cart with a rubber band (this time the stopper will be held in place by the rubber band) 4.Ask the students what they observed and why it happened. 5.Ask the students to think of real life situations where this concept is employed. (seat belts in cars, child car seats, seat restraints on roller coasters, etc)

Demo 2 Balloon

Teacher instructions 1.Obtain a balloon. 2.Blow balloon up. 3.Release balloon. 4.Ask students what happened and why it happened. (Balloon flew around the room because the air was being forced out the nozzle (action) and the balloon was pushed forward (reaction)) 5.Ask students for example in real life where this is demonstrated. (rocket engine, jet engine, kick-back when shooting a shotgun, etc)

Demo 3 Soft foam ball on a string

Teacher instructions 1.Obtain a soft spherical object (foam ball, Styrofoam ball, etc.) 2.Attach a string to the object. 3.Swing the object in a circle above your head while holding the string. 4.Ask the students to make observations. (the object is moving in a circular path around your hand) 5.Ask the student what forces are being applied to the object (centripetal force pulling on the string, gravity pulling down, air resistance) 6.Ask the student what path the object will take if you released it. (It will continue moving away from you in a straight line)

Demo 4 Paper on a Table

Teacher instructions 1.Place a sheet of paper flat on a table. 2.Place fingers on the right and left edge of the paper and push hands together. 3.Ask the students what type of stress is being applied to the paper (compression) and to make observation about what happens. (the paper will bow upward in the middle (simulating mountain building)). 4.Ask students of real life situations where stress is being put on the Earth’s surface and the results. (earthquakes, mountain building)

Review of concepts Fill in the supplied worksheet with the appropriate information from the presentation.

Teacher instructions 1.Hand out handout. 2.Run the Powerpoint on Newton’s Law and have the students fill in information where necessary

Newton’s 1 st Law of Motion - an object in motion will stay in motion and an object at rest will stay at rest unless an unbalanced force acts upon it. (Also known as the Law of Inertia)

Inertia - the tendency of an object to resist any change in motion; the object will remain in motion unless an unbalanced force acts upon it. The more mass an object has, the greater it’s inertia will be.

Which vehicle has more inertia? Which would be harder to push? Which would be easier to stop?

Observe Newton’s 1 st Law in action on the next two slides.

Newton’s Second Law of Motion - a net force acting on an object causes the object to accelerate in the direction of the force. (Also known as the Law of Acceleration)

Force Equation: Force = mass x acceleration or f = ma Units: mass (kg) acceleration (m/s 2 ) force (kg m/s 2 ) or Newtons (N)

Forces that come into play during Newton’s 2 nd Law Friction - the force that opposes motion between two surfaces. Air Resistance – the force air exerts on a moving object Gravity – a force exerted by every object on every other object. (force depends on distance and mass between objects. The greater the mass, the greater the grav. force. The greater the distance, the less the grav. force)

Observe how air resistance cause object to fall at different rates on the next slides.

Elephant and feather with no air resistance.

Elephant and feather with air resistance.

Minimizing air resistance in real life.

Weight – the force of gravity acting on the mass of the object. f = (m) x (a) f = weight a = acceleration due to gravity m/s 2 weight = (mass) x (9.8 m/s 2 )

The mass of an object doesn’t change no matter where you are in the universe but the weight of an object depends on the gravitational pull on that object.

That is why your mass is the same on the moon but your weight is less. Acc. due to gravity on Earth = 9.8 m/s 2 Acc. Due to gravity on the moon = 1.6 m/s 2 EarthMoon Mass 100 kg Weight 980 N160 N

Newton’s Third Law of Motion – for every action force there is an equal and opposite reaction force. (Also known as the Law of Reciprocal Actions)

Which direction will the girl on the skateboard move if she threw the basketball forward? AB C D

Due to Newton’s 3 rd Law she will move backwards. For every action (throwing the ball forward) there is an equal and opposite reaction (skateboard moves back) AB C D

Other situation where Newton’s 3 rd Law come into play.

Other situations where Newton’s Laws are demonstrated in real life.

As magma is forced up through the Earth’s crust it forces the rocks in place to move aside to make room for it.

Earth’s internal forces are constantly changing the Earth’s crust.

Newton’s Law affecting the orbit of planets and satellites.

There is a balance between the gravitation pull of the center object (sun) and the centripetal force on the orbiting objects (planets).

The smaller the mass, the smaller the centripetal force (red vector) you will have to apply to the rope.

The smaller the velocity of the object, the less centripetal force you will have to apply.

The smaller the length of rope (radius), the more centripetal force you will have to apply to the rope. (inner planets move faster because the gravitational pull of the sun is greater)

If you let go of the rope (or the rope breaks) the object will no longer be kept in that circular path and it will be free to fly off on a tangent.

Use your notes over Newton’s 3 Laws of Motion to answer the following questions.

1. Name 3 forces that comes into play with Newton’s 2 nd Law.

2. What is the relationship between mass and inertia?

3. What is another name for Newton’s 2 nd Law?

4. What would the weight of a person who has a mass of 100 kg be (in N) on Mars? Acceleration due to gravity on Mars if 3.7 m/s 2.

5. Which of Newton’s Law is being displayed in this animation?

6. When the space shuttle lifts off the engines are putting out 6 million pounds of thrust. Which of Newton’s 3 Law is being demonstrated by the lifting off of the shuttle?

7. What is the relationship between mass and centripetal force?

8. What force is being minimized in this picture?

9. During an earthquake the Earth’s crust is put under 3 types of stress. (Tension, compression and shearing) The result of this stress is movement of the crust. Which of Newton’s 3 Laws applies to this situation?   tension   compression Shearing

10. If each of these objects were moving at the same speed, which one would have the most inertia? A C B D

Answer Key 1.Friction, air resistance, gravity 2.As mass increases, inertia increases 3.Law of Acceleration N 5.Newton’s 1 st Law 6. Newton’s 3 rd Law 7. The larger the mass, the larger the centripetal force 8. Air Resistance 9. Newton’s 3 rd Law 10. B