PHY 302K Exam 3

Fundamental vs derived properties

Fundamental is measured (time, length, and mass) while derived has to be calculated (volume)

Measurements are based on

Comparison

What is important with measurements

Accuracy and precision

What to compare measurement to

Standard units (SI) = metric systems

3 most fundamental quantities and their unit and symbol

Length: meter (m) mass: kilogram (kg) Times: seconds (s)

what is position

the location of an object; a point; measured by length [m]

What is displacement?

from start point to the end point; measured by length [+/-m]

What is velocity?

Speed in a given direction (length/time)

what is acceleration

rate of change of velocity; speed (length/time^2)

initial and final position notation

displacement can also be described as

change in position

What is a vector?

arrow that includes magnitude (#) and direction (+ or -)

what is distance in reference to displacement

distance = absolute/positive displacement

Δx = ?

change in postion

Δt = ?

change in time

average velocity units

meters/second

average speed is always

positive

what does positive and negative velocity look like graphically

how is average velocity different than instantaneous

same average velocity but different instantaneous

what is instantaneous velocity

the velocity of an object in motion at a specific point in time

instantaneous velocity equation

The smaller the Δt (in instantaneous velocity) the (more/less) instantaneous

more

in changing velocity, instantaneous velocity (=/≠) average velocity

≠

in constant velocity, instantaneous velocity (=/≠) average velocity

=

describe the difference between changing and constant velocity graphically

on a velocity graph what is the relationship between speed and slope

direct

What would a graph look like that an object starts moving slow but then speeds up faster

change in velocity =

acceleration

what are the units for acceleration

m/s^2

if velocity is constant and positive then what does the graph for acceleration look like

constant positive acceleration

if velocity is constant and negative then what does the graph for acceleration look like

constant negative acceleration

instantaneous acceleration equation

as velocity has increased but has now plateaued what is the acceleration doing

decelerating; negative slope

as velocity has increased with a positive slope what is the acceleration doing

constant acceleration ; + straight line

in changing acceleration does instant acceleration (=/≠) average acceleration

≠

in constant acceleration does instant acceleration (=/≠) average acceleration

=

What would constant acceleration look like graphically plotted against time

acceleration is always the same

What would constant acceleration look like graphically plotted against velocity and time

what is the final velocity formula w/ constant acceleration

what is the displacement formula (x) with velocity and acceleration

What would a graph look like that plots displacement against time with an object accelerating

shows the displacement and velocity vectors

what is the displacement formula w/o time

can an object change its direction of travel while maintaining a constant acceleration (direction of acceleration doesn't change)

yes, gravity always pulls down

at a constant acceleration; velocity changes acceleration doesn't; ball thrown up in the air and the

falls down

at the top of a parabola what the the velocity

0

what does displacement, velocity, and acceleration look like graphically for a ball thrown up in the air and falls down (in order)

1) no change in displacement but velocity is (-) and (+)

2) velocity increases, is zero, then decreases

3) acceleration is constant and negative

velocity vector on x and y plane symbol

what axis does gravity affect

Y only (x is not affected by gravity)

how to find Vx from a 2D motion graph

Vx=vcosθ

how to find Vy from a 2D motion graph

Vy=vsinθ

how to find θ from a 2D motion graph

tan^-1 (Vy/Vx)

how to find magnitude (v) from a 2D motion graph

In 2D motion if the resulting vector bends what does it have to have

acceleration/ changing velocity

In 2D motion what does friction change

vector magnitude not the angle of the vector/line

In 2D motion how does gravity behave on a projectile

evenly from the very start

based on pushing a projectile off a surface how do you find the x and y velocities

x velocity is constant (same as initial; a=0 )

y starts as 0 but then is accelerating at -9.8 m/s so use Vy=-gt=at

how does Vy change in a projectile making a parabola

velocity starts at its highest and decreases to 0 as it reaches the peak and then goes negative all due to gravity

how does Vx change in a projectile making a parabola

it doesn't; constant

how does the time to reach the peak relate to the time to hit the ground in a projectile making a parabola

t1=t2

horizontal motion equations for 2D

vertical motion equations for 2D

how does the x direction affect the y

they don't; completely independent from each other

how does the launch angle affect the distance launched

(in 2D projectile motion making a parabola; constant force)

higher the angle the higher the initial velocity and more time spent in the air

what is the optimal launch angle

45 degrees

how to find which projectile will be in the air longer and why

the higher peak will spend more time in the air bc they both fall at -9.8m/s so the shorter peak will reach the ground first

Consider the situation shown here. A projectile is pointed at a person hanging from the gutter of a building. The person lets go and at the same time the projectile gets fired. The initial velocity of the projectile is vo. What happens?

how would you graph the monkey with displacement

second example is with just initial horizontal velocity

how to find total velocity when vectors makes right angle

if I have a velocity vs time graph with a positive constant slope was is happening

increasing velocity, constant positive acc

if I have a displacement vs time graph with a positive constant slope was is happening

constant velocity, zero acc