Forces and MotionForces and Motion

BenchmarksBenchmarks

Standard III - Physical Science

Benchmarks

D. Explain the movements of objects by applying Newton’s three laws of motion.

E. Trace the historical development of scientific theories and ideas, and describe emerging issues in the study of physical science.

Standard III - Physical Science

Benchmarks

D. Explain the movements of objects by applying Newton’s three laws of motion.

E. Trace the historical development of scientific theories and ideas, and describe emerging issues in the study of physical science.

ForceForceForce - a push or a pull exerted on an

object. Units are Newtons (N)Ex: gravity pulls objects to the Earth

Forces can…1. Speed up an object2. Slow down or stop an object3. Change the direction of an object (cause an object to travel in a circle Ex: satellites)

Force - a push or a pull exerted on an object. Units are Newtons (N)

Ex: gravity pulls objects to the Earth

Forces can…1. Speed up an object2. Slow down or stop an object3. Change the direction of an object (cause an object to travel in a circle Ex: satellites)

Force VectorsForce Vectors

Forces have both a magnitude (amount) and a direction, this is called a force vector

Forces can add together or they can cancel eachother out

Forces have both a magnitude (amount) and a direction, this is called a force vector

Forces can add together or they can cancel eachother out

Fundamental ForcesFundamental Forces1. Gravitational Forces - the mass of an object attracts

the mass of another object. Usually the weakest of all forces, but applies to long distances Ex: Weight on Earth, centripetal force

2. Electromagnetic Forces - a charged object attracts or repels another charged object. These forces are stronger. Ex: Friction, electrons, most regular forces

3. Nuclear Forces - two types: strong and weak forces. Occur in the nucleus of a atom and are the strongest forces. Ex: nuclear power and weapons

1. Gravitational Forces - the mass of an object attracts the mass of another object. Usually the weakest of all forces, but applies to long distances Ex: Weight on Earth, centripetal force

2. Electromagnetic Forces - a charged object attracts or repels another charged object. These forces are stronger. Ex: Friction, electrons, most regular forces

3. Nuclear Forces - two types: strong and weak forces. Occur in the nucleus of a atom and are the strongest forces. Ex: nuclear power and weapons

The Force of GravityThe Force of Gravity

The Law of UniversalGravitation

Fgravity = Gm1m2

d2

Fgravity = force of gravity (N)

m1 = mass of 1st object (kg)

m2 = mass of 2nd object (kg)G = gravitational constant (look up)d = distance between object (m)

The Law of UniversalGravitation

Fgravity = Gm1m2

d2

Fgravity = force of gravity (N)

m1 = mass of 1st object (kg)

m2 = mass of 2nd object (kg)G = gravitational constant (look up)d = distance between object (m)

Gravity ContinuedGravity Continued*The force of gravity is directly proportional to the

masses of both object, so if either object has more mass the gravity goes up

*The force of gravity is indirectly proportional to the distance squared between the two objects, so if the distance increases the gravity decreases

*Question: Which effects gravity more the masses of the objects or the distance between them?

*The force of gravity is directly proportional to the masses of both object, so if either object has more mass the gravity goes up

*The force of gravity is indirectly proportional to the distance squared between the two objects, so if the distance increases the gravity decreases

*Question: Which effects gravity more the masses of the objects or the distance between them?

FrictionFriction

Friction - force that resists motion, units are Newtons (N)

Friction increases with the roughness of the surface called mu (µ)

It also increases with the weight of the object

Friction - force that resists motion, units are Newtons (N)

Friction increases with the roughness of the surface called mu (µ)

It also increases with the weight of the object

FrictionFriction Friction increases with the

velocity of the object when traveling through liquids and gases. Ex: skydiving, water skiing

During energy transformations a great deal of the energy is lost to friction in the form of heat energy. Ex: Much of the chemical energy in the gasoline in your car is lost to friction (heat) instead of mechanical energy to make the car move

Friction increases with the velocity of the object when traveling through liquids and gases. Ex: skydiving, water skiing

During energy transformations a great deal of the energy is lost to friction in the form of heat energy. Ex: Much of the chemical energy in the gasoline in your car is lost to friction (heat) instead of mechanical energy to make the car move

Types of FrictionTypes of FrictionThere are four main types of

friction:Sliding friction: ice skatingRolling friction: bowlingFluid friction (air or liquid): air or

water resistanceStatic friction: initial friction when

moving an object

There are four main types of friction:Sliding friction: ice skatingRolling friction: bowlingFluid friction (air or liquid): air or

water resistanceStatic friction: initial friction when

moving an object

Reducing FrictionReducing Friction

Friction can be a good thing (helps us walk) but it can also be a bad thing (reduces effeciency of engines)

Four ways to reduce friction…1. Lubricating between surfaces2. Using ball bearing3. Polishing surfaces4. Using wheels

Friction can be a good thing (helps us walk) but it can also be a bad thing (reduces effeciency of engines)

Four ways to reduce friction…1. Lubricating between surfaces2. Using ball bearing3. Polishing surfaces4. Using wheels

MotionMotion

MotionMotion

Motion - the change in position of an object relative to another object that is assumed to be at rest. Ex: car drives past a sign

Uniform motion - objects travels same speed in a straight line

Motion - the change in position of an object relative to another object that is assumed to be at rest. Ex: car drives past a sign

Uniform motion - objects travels same speed in a straight line

Speed and VelocitySpeed and Velocity

Speed - distance traveled per unit of time, units are meters per second (m/s)

Speed (s) = distance (d) / time (t)s = d/t

Velocity - speed with a direction (same formula, same units as speed)

v = d/t

Speed - distance traveled per unit of time, units are meters per second (m/s)

Speed (s) = distance (d) / time (t)s = d/t

Velocity - speed with a direction (same formula, same units as speed)

v = d/t

Speed and VelocitySpeed and Velocity

If a car traveled 400km West in 4hr, what is the speed and velocity of the car?

s = d/t = 400km/4hr = 100km/hr

v = d/t = 400km/4hr = 100km/hr West

*Velocity is more discriptive then speed

If a car traveled 400km West in 4hr, what is the speed and velocity of the car?

s = d/t = 400km/4hr = 100km/hr

v = d/t = 400km/4hr = 100km/hr West

*Velocity is more discriptive then speed

AccelerationAcceleration

Acceleration is the rate of change in velocity, units are m/s2

Acceleration = final velocity - intial velocitytime

a = vf - vI

t*When an object slows down, it has a negative

acceleration, this is called deccelartion.

Acceleration is the rate of change in velocity, units are m/s2

Acceleration = final velocity - intial velocitytime

a = vf - vI

t*When an object slows down, it has a negative

acceleration, this is called deccelartion.

Falling ObjectsFalling Objects

Falling formulas:v = gt

V = velocity (m/s) g = acceleration of gravity (9.8m/s2)t = time (s)

d = gt2

2d = distance (m) g = acceleration of gravity (9.8m/s2)t = time (s)

*All objects fall at the same rate (g) unless they are slowed by air drag

Falling formulas:v = gt

V = velocity (m/s) g = acceleration of gravity (9.8m/s2)t = time (s)

d = gt2

2d = distance (m) g = acceleration of gravity (9.8m/s2)t = time (s)

*All objects fall at the same rate (g) unless they are slowed by air drag