Physics: Chapter 3 Projectile Motion

Projectile

any object producing a curved motion, only gravity affects it

How far will it land/did it go?

(Horizontal) v=d/t

how to analytically add vectors together?

- find the components of each vector using sin and cos - add x's and y's together - sketch a pic of the x and y component - solve for resultant (hypotenuse) and the angle using tanѲ=y/x

Vertical component of motion

- for objects in freefall - gravity is the only force acting on an object

a shiny new sports car sits in a driveway. a helicopter is now flying directly over the sports car moving at 120 m/s east at a height of 300m. A box falls out of helicopter. Relative to car, where does the box land

- looking for HORIZONTAL distance - find time using d= vit+ 1/2at2 - find distance using v=d/t

Horizontal component of motion

- objects moving across a surface - gravity does NOT affect this motion

how to graphically add vectors together

-move the head of the 1st vector to touch the tail of the 2nd vector -then draw the resultant vector with the tail of the first to the head of the last

At the top of its path y comp

= 0

You can only use vf= vi + at when

PROJECTILE CURVE

air resistance

a force that opposes motion

Vector

a quantity that has both magnitude and direction - represented by arrows - direction pointing is the direction moving - velocity, acceleration, displacement (include direction) - length tells magnitude (longer, more magnitude)

component vectors

a vector that is broken up: on the x and y plane and always perpendicular to each other

Q2 and Q3

add 180

Q4

add 360

how to add scalars

add normally

Resultant

combination of two vectors representing magnitude and direction

How high does the object go

d = vit + 1/2at2 - use 1/2 time - use y comp of velocity

How high was cliff/water?

d= vit + 1/2at2

horizontal component of motion stays constant when?

in the absence of air resistance

Scalar

quantity that only has magnitude - no direction - time, speed, distance

how to (ADD/SUBTRACT) vectors together - remember direction

same direction: add different direction: subtract

if a ball is dropped straight down, and another ball is dropped at the same height with a horizontal speed. which one will hit first and why?

same time because horizontal component is independent from vertical. Since they are both falling from the same height, they will hit at the same time

how does air resistance affect path of projectile

shortens path, projectile will not go as high or as far

a person jumps straight up into air. their hang time is 0.67 s. Same person RUNS and jumps, reaching same height and now travelling a distance of 3.5 m horizontally. What is persons hang time now

still 0.67 s because horizontal speed does not affect vertical distance

resultant vectors

the sum of two or more vectors added together

the common variable between horizontal and vertical equations of motion

time

Component

two parts (vertical and horizontal) of an object in motion

to calculate initial vertical velocity (curve)

use 1/2 time

to calculate initial horizontal velocity (curve)

use full time

Horizontal Equations

v=d/t

gravity only affects which component of motion?

vertical component of motion

Vertical Equations

vf= vi + at vf2=vi2+ 2ad d = vit + 1/2at

How long is it in the air?

vf=vi+at

when something is thrown horizontally, what does the initial velocity equal?

vi=0

asking for velocity as it lands on ground

y comp = negative

you swim across a river and end up down stream due to flow of water. do you move faster that you would if the water did not flow, why?

yes because your total speed = your speed + speed of water