February 8, 2016 Warm-Up: Electricity WS Homework: Read & take notes chapter 18, section 3. USA Test Prep and Skills Tutor #9 due Friday by 4:15. Quiz Thursday: static & current electricity, AC & DC current, series & parallel circuits

February 8, 2016 Warm Up: start Simple Machines WS Homework: USA Test Prep and Skills Tutor #9 due by Test Wednesday: Chapters 5, 6, & 8

SPS8. Students will determine relationships among force, mass, and motion. a. Calculate velocity and acceleration. – Know the difference – Know the units – Know how to solve the problems – Know how to interpret the graphs

Question 1 An object accelerates if its A. Speed remains constant B. Direction changes C. Mass remains constant D. Motion can be plotted on a graph

Question 1 An object accelerates if its A. Speed remains constant B. Direction changes C. Mass remains constant D. Motion can be plotted on a graph

Question 2 Which kind of forces are exerted on an object if there is a net force of zero? A. Unbalanced B. Kinetic friction C. Gravity D. Balanced

Question 2 Which kind of forces are exerted on an object if there is a net force of zero? A. Unbalanced B. Kinetic friction C. Gravity D. Balanced

SPS8. Students will determine relationships among force, mass, and motion. b. Apply Newton’s three laws to everyday situations by explaining the following: 1) Inertia 2) Relationship between force, mass and acceleration 3) Equal and opposite forces – Know real world examples – If given a situation, be able to predict what will happen

Question 3 Which two forces operate to keep a moon in orbit around a planet? A. Inertia and gravity B. Inertia and friction C. Friction and gravity D. Distance and gravity

Question 3 Which two forces operate to keep a moon in orbit around a planet? A. Inertia and gravity B. Inertia and friction C. Friction and gravity D. Distance and gravity

Question 4 A baby pushes on a large chair. What is the reaction force? A. Friction pushes on the chair B. Friction pushes on the baby C. The chair pushes on the baby D. The chair pushes on the floor

Question 4 A baby pushes on a large chair. What is the reaction force? A. Friction pushes on the chair B. Friction pushes on the baby C. The chair pushes on the baby D. The chair pushes on the floor

Question 5 A student kicks a soccer ball across a field. The ball rolls across the field and stops. What causes the ball to stop? A. Gravity acts on it B. Its own inertia stops it C. Friction acts on it D. Balanced forces act on it

Question 5 A student kicks a soccer ball across a field. The ball rolls across the field and stops. What causes the ball to stop? A. Gravity acts on it B. Its own inertia stops it C. Friction acts on it D. Balanced forces act on it

SPS8. Students will determine relationships among force, mass, and motion. c. Relate falling objects to gravitational force – Understand how objects accelerate due to gravity – Understand that the gravitational attraction between two objects depends on MASS and DISTANCE

Question 6 Suppose you roll a basketball and a baseball toward each other. How does this affect the force they exert on each other? A. It increases B. It decreases C. It stays the same D. It disappears

Question 6 Suppose you roll a basketball and a baseball toward each other. How does this affect the force they exert on each other? A. It increases B. It decreases C. It stays the same D. It disappears

Question 7 Which pair of objects will have the LEAST gravitational attraction? A. Two cinder blocks 6 cm apart B. Two marbles 12 cm apart C. A cinder block and a marble 6 cm apart D. A cinder block and a marble 12 cm apart

Question 7 Which pair of objects will have the LEAST gravitational attraction? A. Two cinder blocks 6 cm apart B. Two marbles 12 cm apart C. A cinder block and a marble 6 cm apart D. A cinder block and a marble 12 cm apart Gravitational attraction depends on mass and distance

SPS8. Students will determine relationships among force, mass, and motion. d. Explain the difference in mass and weight. – Know that weight changes if gravity changes, but mass does not

Question 8 Which statement is correct? A. Weight is the amount of material in an object B. Mass is the physical dimensions of an object C. Weight is the gravitational pull on an object D. Mass is the gravitational pull on an object

Question 8 Which statement is correct? A. Weight is the amount of material in an object B. Mass is the physical dimensions of an object C. Weight is the gravitational pull on an object D. Mass is the gravitational pull on an object

Question 9 Your weight on Mars is only about 1/3 your weight on Earth. Which reason BEST explains this? A. Mars is more massive than Earth B. Mars has a smaller force of gravity than Earth C. Mars has a greater force of gravity than Earth D. An object on Mars has less mass than the same object on Earth

Question 9 Your weight on Mars is only about 1/3 your weight on Earth. Which reason BEST explains this? A. Mars is more massive than Earth B. Mars has a smaller force of gravity than Earth C. Mars has a greater force of gravity than Earth D. An object on Mars has less mass than the same object on Earth

SPS8. Students will determine relationships among force, mass, and motion. e. Calculate amounts of work and mechanical advantage using simple machines. – Know the six simple machines – Understand how they help us do work – Know how to calculate work and MA if given the basic versions of the formula – Know units of work, force, and distance

Six Simple Machines Inclined Plane Wedge Screw Lever Pulley Wheel & Axle

Mechanical Advantage

Inclined Plane Reduces force, but increases distance The mechanical advantage of an inclined plane is length divided by height. Wedges and screws are types of inclined planes.

MA = L/H

Wedge A wedge generates outward forces A wedge is a type of inclined plane. Its mechanical advantage is its length divided by its greatest thickness.

Screw A screw is an inclined plane wrapped around a cylinder Uses a small force over a longer distance The closer the threads, the lower the force required

Levers – Three Classes Can change direction & size of force In a first-class lever, the fulcrum is between the force and the load. In a second-class lever, the load is between the force and the fulcrum. In a third-class lever, the force is between the fulcrum and the load.

First Class Lever Change direction & maybe force

Second Class Lever Change force, but not direction

Third Class Lever Don’t change direction, output < input

Pulleys Change direction and may change input force Types of pulleys include fixed pulleys, movable pulleys, and block and tackles.

Wheel and Axle The mechanical advantage of a wheel and axle is the radius of the wheel divided by the radius of the axle.

Compound Machines Compound machines consist of two or more simple machines. Compound machines have low mechanical efficiencies because they have more moving parts and therefore more friction to overcome.

Question 1 Which of the following simple machines is a wedge? A. Wheelbarrow B. Doorknob C. Ax D. Truck ramp

Answer Which of the following simple machines is an example of a wedge? A. Wheelbarrow B. Doorknob C. Ax D. Truck ramp

Question 2 What is the pivot point of a lever called? A. Load B. Fulcrum C. Wedge D. Effort

Answer What is the pivot point of a lever called? A. Load B. Fulcrum C. Wedge D. Effort

Question 3 A student pushes on a lever with a force of 40N. The 150N load does not move. Which of the following is true? A. Input force is 40 N and work done is 0 J. B. Input force is 40 N and work done is 600 J. C. Output force is 40 N and work done is 150J. D. Output force is 150N and work done is 40J.

Answer A student pushes on a lever with a force of 40N. The 150N load does not move. Which of the following is true? A. Input force is 40 N and work done is 0 J. B. Input force is 40 N and work done is 600 J. C. Output force is 40 N and work done is 150J. D. Output force is 150N and work done is 40J.