WEEK 1-2 Grade 8 -first and second LAW OF MOTION.pptx

GRade 8 laws of motion topics

1. Activity 2: Base on the illustration. D ifferentiate the non-contact and contact force.

2. LAW OF MOTION

3. SIR ISAAC NEWTON English scientist and mathematician famous for his discovery of the law of gravity also discovered the three laws of motion.

4. THREE LAWS OF MOTION Newton’s First Law: Objects in motion tend to stay in motion and objects at rest tend to stay at rest unless acted upon by an unbalanced force. Newton’s Second Law: Force equals mass times acceleration (F = ma). Newton’s Third Law: For every action there is an equal and opposite reaction.

5. NEWTON’S FIRST LAW Object at rest tends to stay at rest and an object in motion tends to stay in motion unless acted upon by an unbalanced force

6. LAW OF INERTIA Tendency for an object to stay at rest or moving in a straight line at a constant speed. • The mass (m measured in kg) of an object determines its inertia

7. NEWTON’S SECOND LAW Newton’s Second Law Force equals mass times acceleration. F = ma Acceleration: a measurement of how quickly an object is changing speed.

8. NEWTON’S SECOND LAW The second law states that “when a net force acts on the body, the body will accelerate in the direction of the force. The acceleration is directly proportional to the force. Furthermore, the acceleration is inversely proportional to the mass of the body.

9. NEWTON’S SECOND LAW force and acceleration A force of 50 N accelerates an object by 2.0 m/s2. What is the force needed to give the same object an acceleration of 3.4 m/s2?

10. NEWTON’S SECOND LAW acceleration and mass A certain force accelerates a 3.2 kg mass by 2.4 m/s. what would be the acceleration of 1.6 kg mass when the same force acts on it?

11. WHAT DOES F=ma means? Force is directly proportional to mass and acceleration. 

12. Formula

13. Example Problem A golf ball has a mass of approximately 0.046 kg. How much force must be applied in the tee shot so that the ball will move from rest to 8.25 m/ s in 10.0 s?

14. Example Problem A softball has a mass of 1.5 kg and hits the catcher's glove with a force of 30 N? What is the acceleration of the softball? A 15 kg object moving to the west with an acceleration of 10m/s 2 . What is the net force acting on an object?

15. Example Problem 1. What net force is required to accelerate a car at a rate of 2 m/s2 if the car has amass of 3,000 kg? F=_______ m=______ a= __________

16. Example Problem . A10 kg bowling ball would require what force to accelerate down an alleyway at a rate of 3 m/s2? F=______ m=______ a=______

17. Example Problem 3. Sally has a car that accelerates at 5 m/s2 . If the car has a mass of 1000 kg, how much force does the car produce? F=______ m=______ a=______

18. Example Problem 4. What is the mass of a falling rock if it produces a force of 147 N? F=______ m=______ a=______

19. Everything that moves on Earth follows the Three Laws of Motion. Testing the three laws of motion is endless fun !!! Rube Goldberg Machines!

20. The Challenge • Build a Rube Goldberg machine to demonstrate your understanding of Laws of motion • Use at least 5 simple machines. • Use at least 6 steps and 3 energy transfers. • Write a description of the machine’s steps that identifies and explains each required component of the machine. • Present your Rube Goldberg machine to your peers. !

21. !

22. Today’s Task : Students will spend the rest of the class planning and sketching their design . The teacher can require students to conduct research on different design ideas if time allows . Groups will gather the supplies they will use for their project from the given worksheet. Students may have to change designs depending on available materials. Closure : Groups will submit their Rube Goldberg machine “blueprints” to the teacher.