Newton’s Laws of Motion

Learning Objectives TLW research and describe the history of physics and contributions of scientists (TEKS 3.D / TEKS 3.D) TLW calculate the effect of forces on objects, including law of inertia, relationship between force and acceleration, and nature of force pairs between objects (TEKS 4.D / TEKS 7.B) TLW conduct lab investigations to reinforce principles in a safe manner (TEKS 1 – 3 / TEKS 1 - 6) TEKS Physics / Principles of Technology

Agenda Meet the Man behind the Notion of Laws of Motion Newton’s Laws 1st – Law of Inertia 2nd – Force 3rd – Bodies

I. Sir Isaac Newton A. A remarkable scientist 1. Discovered & proved 3 laws 2. Described the effects of force & motion 3. Newton’s laws are very important 4. He also developed calculus 5. Born on Christmas (12/25/1642 – old calendar)

http://www.biography.com/people/isaac-newton-9422656#synopsis

Video Newton’s Laws of Motion

B. Newton’s 1st Law of Motion 1. Called the Law of Inertia a. States any object at rest will remain at rest * unless acted on by an unbalanced force. b. Any object in motion will stay in motion *unless acted on by an unbalanced force.

c. A car is pushed up a ramp c. A car is pushed up a ramp. The cart moves because an unbalanced force acts upon it. The cart will eventually stop because the force of friction acts against it. If the cart was pushed in space it would continue forever because there isn’t any friction to stop it.

Inertia Inertia is defined as the property of an object to resist changing its state of motion. An object at rest stays at rest or an object in motion stays in motion An object with a lot of inertia takes a lot of force to stop Mass is a measure of the inertia of an object The more mass an object has the greater the inertia and the greater the force needed to change the object’s motion.

e. Ex of 1st law: A car comes to a stop – you still move forward

Force A force is a push or a pull or any action that has the ability to change motion. An object DOES NOT have to move when a force is exerted on it. A force is needed to change motion. Unit is Newton (N) 4.48 N = 1 lbs or 0.22 lbs = 1 N

1. Newton’s 2nd Law says that F=ma C. Newton’s 2nd law 1. Newton’s 2nd Law says that F=ma a. Force causes acceleration b. Mass resists acceleration c. The acceleration you get is equal to the ratio of force over mass

2. The formula for Newton’s 2nd law is Force = mass x acceleration F = ma 3.The second law says that the more mass an object has more force is needed to speed it up or slow it down.

4. How much force is needed to. lift a 200 Kg box upward at 4. How much force is needed to lift a 200 Kg box upward at an acceleration of 5 m/s2 F = ma F = 200 Kg x 5 m/s2 F = 1000 N

A company uses a ramp to slide boxes of parts to a shipping area A company uses a ramp to slide boxes of parts to a shipping area. Each box has a mass of 5 kilograms. When sliding down the ramp, the boxes accelerate at a speed of 0.25 m/sec2. What is the force acting on each box? F = ma F = 5 kg * 0.25 m/s2 F = 1.25 N

6. Ex of 2nd law: Difference between pushing an empty box or a full box masses are different = accelerations different

D. Newton’s 3rd law 1. For every action force, there is an equal & opposite reaction force 2. The law of action & reaction 3. Action & reaction forces occur at the same time 4. The 3rd law operates with force pairs on objects

5. Ex of 3rd law Hammering a nail Hammering is the action Nail is the reaction

II. Free Fall & Weight A. Free Fall- when gravity is the only force acting upon on object 1. the free fall an object is always directed towards the center of the earth 2. free-fall acceleration results from gravity

3. so free fall is abbreviated by the letter g 4. all objects accelerate at exactly 9.8 m/s2 on Earth 5. ALL objects near the Earth’s surface accelerate at the same rate unless there is air resistance

6. So, a 1000 lb. elephant and a. 1 gram feather = will fall at 6. So, a 1000 lb. elephant and a 1 gram feather = will fall at the same rate 7. Why? a. Because of Newton’s 2nd law F = ma b. Heavy objects have greater gravitational force c. but it is harder to accelerate because it has more mass

Galileo’s Gravity Experiment https://www.youtube.com/watch?v=_Kv-U5tjNCY Astronauts Verify Galileo’s Theory https://www.youtube.com/watch?v=5C5_dOEyAfk

Even when things are not moving there are forces acting. b. Gravity pulls the book down with a force. c. The table pushes back up with an equal and opposite force. d. The book stays still because the forces are balanced

Example 2 Which object fell fastest? Which object fell slowest? Which object has the greatest mass? Is air resistance stronger on A or B? Why are the times different? Object Mass (g) Time of Fall (sec) A 5.0 2.0 B 1.0 C 30.0 0.5 D 35.0 1.5

B. Velocity 1. Air resistance and gravity act upon objects 2. When air and gravity are equal the object’s acceleration stops because the air reacts in opposite direction of weight

3. Terminal velocity- is the. maximum velocity of an 3. Terminal velocity- is the maximum velocity of an object occurs when air resistance & weight are equal and the object stops accelerating

4. Ex. sky diving sky diver jumps pulled to Earth due to gravity air resistance increases both gravity & air become equal = terminal velocity of about 200 mi/h

C. Mass vs Weight 1. Mass is the amount of “stuff” or matter of an object. It is a basic property of the object. 2. MASS IS CONSTANT 3. Mass is measured in kilograms (kg) 4. mass always remains the same no matter where you are

5. Weight is the force of gravity on an object. 6. Weight is a type of force 7. WEIGHT CHANGES depending on location 8. Weight is measured in Newtons (N)

Fw = mg 9. Formula for weight Acceleration of gravity 9.8 m/sec2 Weight Force (N) Fw = mg Mass (kg)

10. on the moon you would weigh. very little because there is 10. on the moon you would weigh very little because there is very little gravity BUT your mass would still be the same 11. change in location is a change in weight

Labs Balloon Rockets Adapted from Conceptual Physics Lab Manual pp 55 & 56 (see handout) Determine potential hazards, precautions, PPE needed As an individual, perform the experiment using materials provided Complete calculations and analysis questions

Labs Air Resistance – Parachute IPC Manual Weight, Gravity, and Friction (pp. 20 & 21) Equilibrium, Action, and Reaction (pp. 22 & 23) In Periodic Groups read and understand procedure Set up lab using scientific method Determine potential hazards, precautions, PPE needed