Physics Midterm

Velocity

Vector, quality that refers to "the rate at which an object changes its position."

formula for velocity

V = d/t (m/s)

Acceleration

Vector quality that is the rate at which an object changes its velocity

formula for acceleration

a=vf-vi/t

Speed:

Scalar quantity that refers to "how fast an object is moving"; the rate at which an object covers distance

speed formula

distance/time

Average speed

total distance traveled/total time

Instantaneous speed

the speed of an object at one instant of time

Distance

how far I traveled; scalar

Displacement

how far I am from where I started; vector

Displacement formula

final position - initial position

What is the difference between displacement and distance?

Distance is the amount of ground covered and displacement is the object's overall change in position.

The direction of the acceleration vector depends on 4 things:

whether the object is speeding up or slowing down, if it is moving in the + or - direction

Two examples of positive acceleration

A car speeding up on the highway, a rocket going into the air.

Two examples of negative acceleration

Dropping your phone, a reversing a car in order to park.

What movement is the motion map describing?

The object is moving in the postive directionan at a constant velocity, stops for 3 seconds, and moves at a faster constant velocity in the negative direction.

p-t graphs

Graph that shows the position of an object over a period of time

P-t and v-t graphs moving in the positive direction (straight line)

v-t graph moving in the negative direction

p-t graph moving in the negative direction

Objects traveling with a constant velocity have a ______ line

straight

Objects traveling with a changing velocity have a _______ line

curved

In position-time graphs slope=

velocity

The steeper the slope on a straight line position-time graph...

the faster the velocity

The flatter the slope on a straight line position-time graph...

the slower the velocity

Determining the slope of p-t graph (non honors)

use the slope formula, y2-y/x2-x or rise/run

v-t graphs increasing acceleration

velocity time graph

v-t graphs speeding up (straight line)

v-t graphs slowing down (straight line)

How do you turn a p-t graph into a v-t graph?

Calculate the slope by using slope formula or rise/run

How do you turn a v-t graph into p-t graph

Calculate the area

How do you find the displacement of a p-t graph? (when graph is shaded under)

Break the graph up into shapes, and solve for the area of those shapes

What does the motion map mean? (map on definition page)

The object is moving in the positive direction at a constant acceleration

What do the longer arrows mean in motion maps

More acceleration

What did Aristotle say about motion?

Aristotle said objects will move to a state of rest as that is their desired state.

Why did Copernicus work for years without making his thoughts public?

Copernicus was scared of the backlash he would receive when he went against the Aristotleian thinkers.

Did Galileo make is thoughts public?

Yes, but he was scared of backlash he would recive because his went agaist Aristoleian thinkers. He was placed under house arrest.

Inertia

the resistance of any physical object to any change in its velocity.

What did Galileo do from the top of the Leaning Tower of Pisa, and what did it demonstrate?

Dropped balls of different masses to see which hit the ground first. They hit the ground at the same time, which demonstrated there is some kind of force pulling the balls down at the same rate.

What is a vacuum (in the terms of science)?

A space devoid of matter

How does the slope of a ramp affect the distance a ball travels down the ramp?

The steeper the slope is, the more distance the ball will cover. The flatter the slope, the less distance the ball will travel.

Law of Inertia

Every object continues in a state of rest or of uniform speed in a straight line path unless acted on by a nonzero force.

Why do you launch forward in a car at rest if it's hit from behind?

Your body will try to stay at rest but the car is being moved due to being hit from behind, so you launch forward.

Newtons 1st Law?

An object at rest stays at rest and an object in motion stays in motion unless acted upon by an unbalanced force.

Force

a push or pull, friction, tension, gravity, support/normal

Net force

the sum of all forces acting on an object (positive and negative)

Vector

an arrow drawn to show length and direction of a force

Vector Quantity

requires both magnitude and direction

Scalar Quantity

requires magnitude only

The Equilibrium Rule

An object is in mechanical equilibrium whenever the net force on the object is zero, is at rest, or is moving at a constant velocity.

Support Force (aka Normal Force or Fn)

A force that pushes up on something; usually equals the weight of the something.

If an object is under the influence of only one force, can it be in equilibrium?

No, if only one force is acting on an object, the forces are unbalanced, and therefore not in equilibrium.

Support/normal force

the force that pushes up on something; usually equals the weight of the something.

Newton's 2nd Law Formula

F= m x a

Finding mass using Newton's 2nd Law formula

m= f/a

Finding acceleration using Newton's 2nd Law formula

a=f/m

Newton's 2nd Law

The acceleration of an object depends on the mass of the object and the amount of force applied.

If an object has more mass, will it have more or less acceleration?

Less acceleration

If an object has less mass, will it have more acceleration or less?

More acceleration

Friction

Usually reduces net force and the resulting acceleration of an object; Caused by irregularities in surfaces that are in contact.

Friction depends on..

The kinds of material and how much they are pressed together.

The direction of friction is always...

opposite the direction of motion

An object at rest experiences how much friction..?

None

Static friction

Friction that builds up before sliding takes place

Sliding friction

Friction that occurs between two surfaces sliding past each other

Mass

quantity of matter in an object

Weight

The force on an object due to gravity

Formula for weight

w= m x g

What is the force of gravity on Earth?

10 m/s^2

Fapp

Applied force

Fn

normal or support force

Fg

Gravity

Fair

air resistance

Ft

tension force

When is Ft present?

When an object is hanging from a string

Free Fall

a state in which something falls due to gravity only

Air drag

Resistance to free fall caused by air (parachute)

Newton's 3rd Law

For every action there is an equal and opposite reaction

In NLM3, as mass increases..

acceleration decreases when force is constant

Why is the acceleration of a bullet greater then the acceleration of a gun ? (short answer question dont even try typing allat)

Newtons 2nd law states that F=ma. So the force is determined by the mass and acceleration of the object. Newton's third law says that for every action there is an equal and opposite reaction. The force that the bullet feels from the gun, is equal in magnitude and opposite direction from the force that the gun feels from the bullet. Because the forces are the same, with an equal force but less mass, there is going to be more acceleration (bullet). Where as for an equal force but more mass the gun feels less acceleration (gun).

A boxer can hit a heavy bag with great force. Why can't he hit a piece of tissue paper in the air with the same amount of force? (short answer question dont even try typing allat)

When a boxer hits a heavy bag, the bag resists the punch. So because of NLM3 the bag exerts and equal and opposite force back on the boxer. A piece of tissue paper offer almost no resistance. When the boxer tries to punch it the tissue simply accelerates away or tears instead of pushing back significantly. The tissue does not exert a large force back, so the boxer cannot exert a large force on it.

Density formula

mass/volume

Characteristic of Atoms

Tiny, neutral, make up everything

Pure substances are either __________ or ___________. There is only one way to make them.

elements and compounds

Mixtures

a physical combination of substances; homogenous and heterogenous

Elements

Atoms of the element itself, nearly all of them are remnants of stars, arranged by atomic numbers

Compounds

2 or more different elements chemically combined

Example of compound

salt

homogeneous mixtures

a mixture that is the same throughout

Example of homogenous mixture

Coffee (you dont see individual sugar pieces + milk)

heterogeneous mixture

mixture that is different through

Example of heterogenous

soil

Molecule

two or more atoms chemically combined, can be two different or two same atoms; pure

Example of molecule

H2O

Proton

positive charge; in the nucleus

Neutron

no charge; neutral; in the nucleus

Electron

negative charge, outside nucleus

On the periodic table of elements the atomic number is the same as..

the protons and the electrons

On the periodic table of elements, the formula to calculate the mass is..

Protons + neutrons

Formula to find how many neutrons a element has

atomic mass-atomic number