Newton’s Laws of Motion Red - Write it 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 Blue - Highlight it
1. Motion: A change in Position
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. Velocity
Speed: distance traveled divided by the time needed to travel.
Velocity: displacement (although distance is usually used) divided by time including direction of travel.
Formula: s = d/t
Mathematically, Speed and Velocity are the SAME; Velocity adds a direction
3.Graphing Speed: distance over time
Constant Speed (top)
As the time changes, the distance changes.
The steeper the slope, the faster the speed (more distance in less time).
The shallower the slope, the slower the speed (more time to cover less distance).
Object at rest (bottom)
As the time changes, the distance remains unchanged.
Acceleration: change in velocity divided by the time needed for the change.
Since acceleration is a change in velocity ,
If you change direction, even without changing speed, you are accelerating!
Slowing down is also considered acceleration! It is called negative acceleration .
Formula: (final velocity – initial velocity)
5. Graphing Acceleration: velocity over time
Section A: acceleration
Section B: no acceleration; constant velocity
Section C: negative acceleration
6. Newton’s Laws of Motion
To understand Newton’s Laws:
Force: a push or pull with a size and direction.
Balanced forces: 2 forces that are equal but in opposite directions, canceling each other out.
Unbalanced forces: when one force is greater than another, causing a change in motion.
Measured in newtons, N .
7. 1 st Law of Motion
Objects resist changes in motion!
If an object is at rest, it will stay at rest*
If an object is in motion, it will stay in motion*
*Unless acted on by a force!
Also known as: The Law of Inertia
More mass = more inertia
8. 2 nd Law of Motion
An object acted on by an unbalanced force will accelerate in the direction of the force.
Mass (m) & Acceleration (a) affect force (F).
Formula: F = ma
When falling, acceleration is due to gravity and is a constant: 9.8 m/s 2
9. 3 rd Law of Motion
For every action, there is an equal but opposite reaction.
When a force is exerted on an object, the object exerts the same amount of force.
10. Force of Gravity: Mass V. Weight
The amount of matter an object has, regardless of any outside force being applied.
On the Moon, your mass would remain the same, but your weight would change.
The force of gravity multiplied by mass.
An object’s weight can change, depending on the pull of gravity.
On Earth, it’s calculated as mass X 9.8 m/s 2
Measured in Newtons.
Gravity: the force of attraction that exists between any two objects that have mass.
11. Friction: A. a force that resists motion & is always present between 2 moving surfaces
Rolling friction: friction between a surface and a wheel as the wheel rolls.
Sliding friction: friction that occurs when 2 surfaces slide past each other, slowing down the moving object.
Static friction: Friction that hinders a stationary object from moving on a surface when a force is applied.
12. Air Resistance: A special form of Friction
Why does the feather fall more slowly than the elephant?
Acceleration due to gravity is constant at 9.8 m/s 2 ; therefore, the elephant should hit with a stronger force, but not faster.
The action of air molecules ‘catch’ on the surface area of an object and slow it down.
According to Galileo, without air resistance, both objects would hit the ground at the same time!
B. Galileo proved right!
While on the Moon, the Apollo astronauts proved Galileo correct.
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/s 2
Acceleration is not affected by the mass of the object!