Unit 1

Question 1

Vector quantity

Answer 1

a physical quantity that has both magnitude and direction

Question 2

Magnitude

Answer 2

the distance of a quantity from zero

Question 3

Physical quantity

Answer 3

a property of a system that can be quantified by measurement

Question 4

Direction

Answer 4

orientation or path of an object’s motion

Question 5

Examples of vector quantities

Answer 5

displacement, velocity, momentum

Question 6

System

Answer 6

collection of objects that are being studied together (e.g. sled and person on sled, single electron interacting with EM field)

Question 7

Open system

Answer 7

Can exchange both matter and energy with surroundings (e.g. human body (waste and energy, such as food and oxygen, is transferred))

Question 8

Closed system

Answer 8

Can exchange energy with surroundings but not matter (e.g. covered pot on stove with boiling water (heat can transfer but water cannot))

Question 9

Isolated system

Answer 9

neither exchanges matter nor energy with surroundings (e.g. insulated water bottle (neither heat nor matter is exchanged with surroundings))

Question 10

Force

Answer 10

when an object experiences a push or pull that causes a change in its motion. Force is a vector quantity, having both magnitude and direction

Question 11

Equation for force

Answer 11

F=ma
-a: acceleration (m/s^2)
-m: mass (kg)
direction of acceleration is always same as direction of force

Question 12

Gravitational force

Answer 12

force object experiences due to gravity, produces constant acceleration of 9.8 m/s toward surface of earth

Question 13

Energy

Answer 13

the capacity to do work and exert force that causes and object to move or change its state, measured in Joules (J) (e.g. potential, kinetic, electrical, thermal, etc.)

Question 14

Kinetic Energy (KE)

Answer 14

the energy of an object that is associated with its motion (e.g. throwing a ball, shooting arrow, falling, flying airplane) (never negative)

Question 15

Formula for Kinetic Energy

Answer 15

KE=1/2mv^2
-m: mass (kg)
-v: velocity (m/s)

Question 16

Potential Energy (PE or V)

Answer 16

the energy stored in an object due to its location relative to a specific reference point (e.g. raised object, dynamite, drawn bow, stretched spring, battery, etc.)

Question 17

Law of Conservation of Energy

Answer 17

the total energy of an isolated system remains constant (Etot). An isolated system’s kinetic energy changes as the magnitude of its velocity changes, while its potential energy changes as its position changes.

Question 18

Total Energy equation

Answer 18

Etot= KE + Vr
kinetic + potential energy

Question 19

Electrical force (F(r))

Answer 19

the attractive or repulsive force that exists between two objects, the force that charged particles exert on each other. Charge of a particle has both sign and magnitude.

Question 20

Charge of negatively charged particle

Answer 20

-1.602x10^-19 C

Question 21

Charge of positively charged particle

Answer 21

1.602x10^-19 C

Question 22

Electrical force equation (F(r))

Answer 22

F(r)= (q1q2)/4piE0r^2
-q1: charge on 1st particle
-q2: charge on 2nd particle
-E0: permittivity of vacuum (8.854x10^-12)
-r: distance between particles

Question 23

Permittivity of a vacuum

Answer 23

A measure of how dense of an electric field is permitted to form in response to electric charges, relates units for electric charge into length and force

Question 24

Electric field

Answer 24

the physical field that surrounds electrically charged particles. Charged particles exert attractive forces when opposite signs and exert repulsive force when same signs

Question 25

Coulomb's law

Answer 25

the greater the magnitude of the charges, the greater the force

Question 26

Formula for Coulombic Potential Energy (V(r))

Answer 26

V(r)= (q1q2)/4piE0r

Question 27

Coulombic Potential Energy (V(r))

Answer 27

the stored energy of a system of two charged [articles interacting, varies as distance between particles, r, varies

Question 28

How Coulombic potential changes with same/opposite sign particles

Answer 28

V(r)>0 when same sign V(r)<0 when opposite sign

Question 29

Coulombic force

Answer 29

F(r)= -d(V(r))/dr (negative first derivative of V(r)) or F(r)= (q1q2)/4piE0r^2 (positive=repulsive, negative=attractive)

Question 30

Electric field lines

Answer 30

point radially outward from a positive charge and inward to a negative charge, never cross, strength of field is related to number of lines per unit

Question 31

Force of electric field

Answer 31

F=qE -q: charge of particle -E: electric field vector (N/C)

Question 32

Cathode-ray experiment

Answer 32

J.J. Thomson, put metal cathode and anode in an enclosed and evacuated tube, made cathode rays emit from cathode (negatively charged) into anode (positively charged) with hole in center, causing them to go in straight line between electric field plates. With electric field turned on, the cathode-ray was deflected in opposite direction of applied E field. Magnetic field deflected cathode-rays back to center. Different metal cathodes gave same results.

Question 33

Results of cathode-ray experiment

Answer 33

-Because rays could be deflected by magnetic field, Thomson concluded the particles were charged. -By measuring deflection of cathode rays in both electric and magnetic fields, was able to calculate charge-to-mass ratio of particles. -Cathode ray behaved as negative particles. -Atoms of different elements must contain both negative and positive charges

Question 34

Cathode

Answer 34

negatively charged electrode by which electrons enter a device

Question 35

Anode

Answer 35

positively charged electrode by which electrons leave a device

Question 36

Electrode

Answer 36

a conductor through which electricity leaves or enters an object, substance, or region

Question 37

Millikan oil-drop experiment

Answer 37

Began with a chamber with two parallel metal plates, and fine mist of oil droplets are sprayed though hole in top plate. Air is ionized, allowing electrons to attach to oil droplets and give them negative charge. By adjusting the voltage applied to the plates, the electric force acting on a droplet can be balanced against the gravitational force, causing it to remain suspended in midair.

Question 38

Results of millikan oil-drop experiment

Answer 38

-by measuring the voltage needed to suspend a droplet and knowing its mass, millikan could calculate charge of electron (-1.602x10^-19)

Question 39

mass-to-charge ratio

Answer 39

mg=qE -m: mass of particle (kg) -g: force of gravity -q: charge of particle -E: force of electrical field

Question 40

J.J. thomson's plum pudding model

Answer 40

electrons were embedded in a diffuse positive matrix of positive charge

Question 41

Rutherford's alpha particle (gold foil) experiment

Answer 41

positively charged particles (alpha (He2+)) were fired at thin sheet of gold foil. most particles passed straight through, but some were deflected at large angles of 90 to 180 degrees, leading to conclusion that atoms have a tiny, dense, positively charged nucleus at their center