projectile motion new

7/17/2019 Projectile Motion New

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ProjectileMotionProjectile motion.

Efect o air resistance onprojectile motion.



What is a projectile? Any object that moves through the air or

space



First… et!s thin" about objects that move

hori#ontal…



$ori#ontal Motion % there &ere no

gravity' an object

movinghori#ontally (in the)*+irection, &oul+continue to move

in a straight line



-ertical Motion % an object is

+roppe+ vertically

(in the y*+irection,' thengravity causes itto accelerate

+o&n&ar+s



Projectile MotionProjectile motion is a combination o hori#ontal an+ vertical

motion

%n the )*+irection' it continues to move at a constant spee+' butin the y*+irection' it accelerate +o&n&ar+s because o gravity



%mportant points.. For a projectile/ 0$E 1*-E23%04 %5

independent 2F 0$E 4*-E23%04

0he spee+ in the )*+irection doesn’tcare &hat the spee+ in the y*+irectionis



6emember that gravity is only pulling in one +irection(+o&n&ar+s, an+ nothing is pulling left or right

% there &ere no gravity' a projectile &oul+ go in a straightline orever/

%mportant points..



-elocity -ectors 6emember that velocity has a magnitude and

direction' so it can be represente+ using vector.

We can brea" +o&n the velocity into separate )*

an+ y* components/



$ori#ontal motion %gnoring air resistance' no net horizontal

force acts on the object.

2bject move &ith uniform velocity Fnet 7 8 thereore acceleration = 0

(F=ma)

E9uation relate+ to hori#ontal motion

S x = U x t

S x =horizontal displacement

U x =initial horizontal velocity

t= time



$ori#ontal motion

R=U x T

R76ange (Ma) hori#ontal +isplacement,

Ux7initial hori#ontal velocity

7time o projectile (time projectilespen+s in the air

6



-ertical motion Projectile un+ergoes vertical

acceleration +ue to gravitational

acceleration E9uation relate+ to vertical motion

:



-elocity -ectors et!s e)amine the ) an+ y velocity vectors or a

projectile/

!x is uniform

!y is

increasing



<ust li"e in ree*all/

-elocity in the y*+irection decreases on the &ay up'

an+ increases on the &ay +o&n

At the top o the path' the y*velocity is al&ays zero

-elocity on the &ay up e"ual velocity on the &ay +o&n

&hen you reach the same height

#0ms$

%

&0ms$

%

%0ms$

%

0ms$%

%0ms$

%

&0ms$

%

#0ms$

%



0est yoursel… An airplane is carrying a bomb an+

traveling &ith a velocity o ='=88 mph

east. % it releases its bomb an+continues at that velocity' &ill the bomblan+/ A. >irectly un+erneath the plane

. ehin+ the plane 3. Ahea+ o the plane



Ans&er

% they!re going at the same )*velocity' it&ill lan+ +irectly beneath the plane



0est yoursel…. 5uppose t&o balls release+

rom the same height/ oneis +roppe+ rom rest' an+the other is thro&n

hori#ontally. Which &ill hitthe groun+ @rst? Why?

0hey &ill hit at the sametime' because they are

both being pulle+ bygravity at the same rate2nly one &ill have agreater )*range.



Ma)imum range6ange is the hori#ontal +isplacement

6ange +epen+ on/ 0he angle that the projectile is launche+ at.

0he velocity it is launche+ at.



E A3 AF0E6 5$260 -%>E26EA…..

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http://www.youtube.com/watch?v=zEHLN06NkiY






E)ample =A gol ball o mass g is hit hori#ontally rom the top o a 8.8m high clif&ith a spee+ o :ms*=.Assuming an acceleration +ue to gravity oG.H8ms*: an+ ignoring air resistance' calculate

a, 0he time that the ball ta"es to lan+

b, 0he +istance that the ball travels rom the base o the clif

c, 0he velocity o the ball as it lan+s

+, 0he net orce acting on the ball at points A an+

e, 0he acceleration o the ball at point A an+

, 0he +isplacement o the ball ater :.88s



E)ample : A D "g athlete in a long jump event leaps &ith a velocity o I.8 ms *= atJ8.8K to the hori#ontal. 0reating the athlete as a point mass' ignoring airresistance' an+ using g as G.H8 ms*:' calculate/

a, the hori#ontal component o the initial velocity

b, the vertical component o the initial velocity

c, the velocity &hen at the highest point+, the ma)imum height reache+ by the athlete

e, the total time or &hich the athlete is in the air

, the hori#ontal +istance travelle+ by the athlete!s centre o mass(assuming that it returns to its original height,

g, the athlete!s acceleration at the highest point o the jump



0hat!s all or to+ay.. 5EE you in lab session tomorro&

pBs / ong holi+ay on the &ay …

'R*+++++++( 0hurs+ay L Mon+ay,

>on!t orget your home&or"s…

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Efect o air resistance onprojectile motion

Path o projectilei no air

resistance(parabolic,Path i air

resistance ispresent




0ime ta"en or its up&ar+ path isshorter than time ta"en or its+o&n&ar+ path 0=N0: W $ 4

?

? ?..

t== t:=




mgirresistance

b,ect

movingup

irresistance

b,ectmoving do-n

mg

.ote / ir resistance is al-ays opposite to

motion

he net force is less on the-ay do-nhe smaller accelerationmeans a greater time ta1en tocover the same distance

t== t:=




%n conclusion' projectile motion in air

a,re+uce its range

b,re+uce its ma)imum height

c,increase its angle o +escent

Path o projectile

i no airresistance(parabolic,Path i air

resistance ispresent



Efect o air resistance on

projectile motion

Factors that efect air resistance

2ilhouette rea …bigger the cross

sectional area bigger the air resistance3ass…2maller the mass' bigger the air

resistance

Eg / table tennis ball e)perience more

resistance than shot putt.

projectile motion new

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