Teks:

8.6a- Demonstrate and calculate how unbalanced forces change the speed or direction of an object in motion

8.6b- differentiate between speed, velocity and acceleration

1. Motion: A change in 1. Motion: A change in PositionPosition

A. Distance vs. Displacement

1. Distance: the entire path of travel OR how far you went.

2. Displacement: the straight line measurement (distance) between starting & ending points (including direction).

2. Speed vs. Velocity2. Speed vs. Velocity

A. Speed: distance traveled divided by the time needed to travel.

B. Velocity: displacement (although

distance is usually used) divided by time including direction of travel.

C. Formula: s = d/t D. Mathematically, Speed and Velocity

are the SAME; Velocity adds a direction

3.Graphing 3.Graphing Speed:Speed:

distance over distance over timetimeA. Constant Speed (top)

1. As the time changes, the distance changes.

2. The steeper the slope, the faster the speed (more distance in less time).

3. The shallower the slope, the slower the speed (more time to cover less distance).

B. Object at rest (bottom)1. As the time changes, the

distance remains unchanged.

4. Acceleration4. AccelerationA. Acceleration: change in velocity divided

by the time needed for the change.B. Since acceleration is a change in

velocity, C. If you change direction, even without

changing speed, you are accelerating!D. Slowing down is also considered

acceleration! It is called negative acceleration.

E. Formula: (final velocity – initial velocity)time

5. Graphing Acceleration:5. Graphing Acceleration:velocity over timevelocity over time

A. Section A: accelerationB. Section B: no acceleration; constant velocityC. Section C: negative acceleration

6. Newton’s Laws of Motion6. Newton’s Laws of Motion To understand Newton’s

Laws:A. Force: a push or pull with a

size and direction.1. Balanced forces: 2 forces

that are equal but in opposite directions, canceling each other out.

2. Unbalanced forces: when one force is greater than another, causing a change in motion.

B. Measured in newtons, N.

7. 17. 1stst Law of Motion Law of MotionA. Objects resist changes in motion!

1. If an object is at rest, it will stay at rest*2. If an object is in motion, it will stay in

motion**Unless acted on by a force!

B. Also known as: The Law of Inertia1. More mass = more inertia

8. 28. 2ndnd Law of Motion Law of Motion

A. An object acted on by an unbalanced force will accelerate in the direction of the force.

1. Mass (m) & Acceleration (a) affect force (F).

2. Formula: F = ma3. When falling, acceleration is due to

gravity and is a constant: 9.8 m/s2

9. 39. 3rdrd Law of Motion Law of Motion

A. For every action, there is an equal but opposite reaction.

1. When a force is exerted on an object, the object exerts the same amount of force.

10. Force of Gravity: Mass V. 10. Force of Gravity: Mass V. WeightWeight

B. Mass1. The amount of matter

an object has, regardless of any outside force being applied.

2. On the Moon, your mass would remain the same, but your weight would change.

C. Weight1. The force of gravity

multiplied by mass.2. An object’s weight

can change, depending on the pull of gravity.

3. On Earth, it’s calculated as mass X 9.8 m/s2

4. Measured in Newtons.

A. Gravity: the force of attraction that exists between any two objects that

have mass.

11. Friction:11. Friction:A. a force that resists motion & is always

present between 2 moving surfaces

1. Rolling friction: friction between a surface and a wheel as the wheel rolls.

2. Sliding friction: friction that occurs when 2 surfaces slide past each other, slowing down the moving object.

3. Static friction: Friction that hinders a stationary object from moving on a surface when a force is applied.

12. Air Resistance: 12. Air Resistance: A special form of A special form of

FrictionFrictionA. Why does the feather fall more

slowly than the elephant? 1. Acceleration due to gravity is

constant at 9.8 m/s2; therefore, the elephant should hit with a stronger force, but not faster.

2. The action of air molecules ‘catch’ on the surface area of an object and slow it down.

3. According to Galileo, without air resistance, both objects would hit the ground at the same time!

B. Galileo proved B. Galileo proved right!right!

1. While on the Moon, the Apollo astronauts proved Galileo correct.

2. Although they dropped a hammer, not an elephant, the two objects landed at the same time.

C. Acceleration due to gravity is a constant – 9.8 m/s2

D. Acceleration is not affected by the mass of the object!

E. (but slowing down is effected by air resistance)

Special note:Special note:

Answer to number 6 on page Answer to number 6 on page 22:postiive22:postiive