Physical Science Exemption Exam Practice

4 Ways to Gain Knowledge

1. Authority

2. Intuition

3. Sensory Data

4. Reason

6 Self Evident Truths

1. Existence

2. Time Symmetry

3. Position Symmetry

4. Occam's Razor

5. Non-contradition

6. Causality

The Scientific Method

1. Hypothesis

2. Theory

3. Law

4. Model

Rocks are held together by…

Electromagnetic interactions

Galaxies are held together by…

Gravity

Newton's First Law:

I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

Essectially Galileo's concept of inertia ("Law of Inertia")

Example: If something is in motion it will stay in motion unless there is an outside force to act upon it

Newton's Second Law of Motion:

F = ma.

Newton's Second Law (connections)

This is the most powerful of Newton's three Laws, because it allows quantitative calculations of dynamics: how do velocities change when forces are applied. Notice the fundamental difference between Newton's 2nd Law and the dynamics of Aristotle: according to Newton, a force causes only a change in velocity (an acceleration); it does not maintain the velocity as Aristotle held.

*This is sometimes summarized by saying that under Newton, F = ma.

Newton's Third Law of Motion:

For every action there is an equal and opposite reaction.

Example: stepping off a boat onto the bank of a lake, as you move towards bank, the boat moves away from the bank.

Velocity vs. Acceleration

Velocity: speed (faster slower) and direction (centripetal acceleration: orbits, turning cars etc.)

Acceleration: a change in velocity

Forces vs. Net Force

Net Force: the sum of all forces acting on an object.

An object can have multiple forces acting on it but there is only one net force.

Net force and acceleration are ALWAYS in the same direction

Types of Net Force

The sum of all forces acting upon an object

1. Balanced force: no net force (uniform motion)

2. Unbalanced forces: net force (accelerated motion)

3. No net force: no acceleration

w =

mg

Pressure =

Force/Area

Density =

Mass/Volume

Practice: If a semi and a cooper collide…

they exert the same forces on each other. But the cooper will accelerate backward more because its greater mass (This is an example of Newton's 3rd law)

Practice: You are in a rotating cylinder wearing roller skates. What are the forces upon you?

1. Gravity

2. Contact force: you are pushing on the floor and the floor is pushing back on you.

Practice:What are the forces, velocities, and acceleration upon you as you ride an elevator?

(Before you move the forces are balanced)

1. Gravity

2. Contact force

(As the elevator accelerates you have to overcome gravity, so the contact force has to overcome gravity)

3. As you move between forces you are in uniform motion again.

(As you stop Gravity must overcome contact force)

Practice: You are sitting in a chair. What is the reaction force to gravity pulling on you that is required by Newton's 3rd Law?

If the earth is pulling on you you must be pulling back on the Earth.

What can you say about an object's weight and mass as it moves farther from the earth?

1. Mass stays the same/Constant

2. Weight decreases: if you are further away from the earth the object's gravity has less pull on you.

Practice: What are the forces on a car passenger as it turns a corner at a constant speed?

1. Centripetal force: you are accelerating because this force makes you change direction.

2. Gravity

3. Contact Force

Circular motion is…

Acceleration or a single force pulling inward.

Practice: You have two charged balls that are one meter apart. How does the force on either ball change if you bring them closer together so that they are now 0.5m apart.

1. It gets stronger

2. You do not need to know the change on the balls for electrical force. It is ALWAYS strongest when they are closer together no matter if the force is repulsive or attractive.

3. Fe=KQq/d^2

Practice: You have two charged objects one meter apart. How does their potential energy change if you decrease the separation by half to 0.5m?

1. NOT enough information. Are the charges the same or different?

2. The electrical force depends on distance: lower the distance the greater the force.

3. Potential energy DEPENDS on the charges: repulsive: potential energy will be greater when they are farther apart. attractive: potential energy will be greater when they are closer together.

(5 Predictions) Objects moving at a high speed as observed from a "stationary" frame of reference are measured to be…

1. Short (length contraction)

2. Fat (mass increase) … e=mc2

3. Slow (time dilation)

4. Simultaneity

5. Conservation of mass and energy together

Types of Conservation

1. Conservation of mass

2. Energy

3. Mass number

4. Charge

5. Linear Motion

6. Conservation of mass and energy are only conserved together at a night speed. Otherwise consider mass and energy to be conserved separate.

Energy Transformations: A jumping frog: How does it happen?

1. Chemical potential energy (ingested food)

2. Elastic Potential energy (muscles)

3. Kinetic energy (the jump upwards)

4. Gravitational potential energy

5. Kinetic energy (coming down)

6. Thermal energy (dissipated through ground)

Heat Transfer

1. Conduction

2. Convection

3. Radiation

Forces in Fluids

(Fluids: anything that flows)

1. Bounded: Lakes tubs, tubes etc.

2. Pressure: bounded: equalizes to all points. unbounded: depends on depth ONLY

3. Buoyant Force: Weight of Displaced water (determined by the object's volume). BF is always UP because the greater pressure comes from the lower depth. Buoyant force is affected ONLY by the VOLUME of the object. Depth and Weight do not mater.

Whether an object will float or sink depends on the net force.

Mass of two falling balls

1. Mass has nothing to do when an object hits the ground, only depends on how close the object is to the earth.

2. Bigger mass= greater force of gravity

3. Balls will hit the ground at the same time

When does the gravity really go to zero?

NEVER

Change in distance will effect…

Change in distance will effect a change in force and vice versa

What are the 4 Types of Waves?

1. Compression Longitudinal

2. Transverse Shear

3. Surface Waves

4. Standing Waves

Standing Waves

When a wave combines back on itself by reflecting or wrapping around.

Surface Waves

Waves that travel along the surface of a medium

Transverse Shear Waves

waves that can only go through solids

Compression Longitudinal Waves

waves that can go through all states of matter: solids, liquids, gas, and plasma.

What are the 4 Wave Properties?

1. Amplitude

2. Wavelength

3. Frequency

4. Speed