Launching aircraft by steam

Did you know jet fighters are sometimes powered by steam? On aircraft carriers, jet fighters are launched from the deck by means of a steam catapult, which helps accelerate the aircraft quickly enough to achieve takeoff speed in the short distance of the carrier deck. The necessary takeoff speed for a modern carrier based fighter is 80 m/s 80~\mbox{m/s} and the length of the steam catapult on a carrier deck is around 95 m 95~\mbox{m} . If the acceleration of the jet from rest is constant, what is the minimum acceleration the catapult must provide during takeoff in m/s 2 \mbox{m/s}^2 ?


The answer is 33.68.

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11 solutions

Sadman Sakib
Nov 10, 2013

By the Equation of motion, v 2 = u 2 + 2 a s v^2 = u^2 + 2as

where v v is the final velocity , u u is the initial velocity , a a is the acceleration and s s is the displacement .To get the minimum acceleration we are considering the greatest displacement that is 95 95 m . As the jet starts from rest u = 0 u = 0 .

a = v 2 u 2 2 s \displaystyle a = \frac{v^2 - u^2}{2s} ,by the equation

= 8 0 2 0 2 2 × 95 \displaystyle =\frac{80^2 - 0^2}{2 \times 95}

= 33.684 =\boxed{33.684}

What is v^2 (if that is a v) and what is u^2 (if that is a u)? Are these the final and initial velocity? Please help.

Jehozaphat Castillo - 7 years, 7 months ago

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you're right. v stands for final velocity and u stands for initial velocity. v^2 and u^2 means the square of v and u respectively.

Apoorva Singh - 7 years, 7 months ago

v^2 - u^2 = 2as

v=final velocity = 80 m/s

u=initial velocity = 0 m/s

s=distance=95m

Therefore, a=acceleration=(6400/(2*95))=3200/95

Akbarali Surani - 7 years, 7 months ago

but I know that a = (V2 - V1)/(t2 - t1) what happened to this equation

Oussama Jaber - 7 years, 7 months ago

what is the u Mean ??? v is for Vector right ! and A is for Acceleration of the object !

Jhay-ar CLink'z - 7 years, 6 months ago

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V is for Velocity and A is for acceleration that's right.

Oussama Jaber - 7 years, 6 months ago

Work done=Change in ke!.........mar=1/2mv^2....

Harikrishna Menon - 7 years, 1 month ago

why doesnt velocity=displacement/time applicable?i get the time from this equation and divide it to velocity and get wrong

Cham Han - 7 years, 6 months ago

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You mean v = s t \displaystyle v = \frac{s}{t} . But that’s only applicable when there’s no acceleration,you get it ?

Nowshin Nawar - 7 years, 6 months ago

a stone is tied to a string and is rotated horizonally, name the force that provides the centripetal force t the string

shashank reddy - 7 years, 2 months ago
Mohith Manohara
Nov 11, 2013

d = u t + 1 2 a t 2 d=ut+\frac{1}{2}at^{2}

v = u + a t v=u+at

Plugging in numbers we get

95 = 1 2 a t 2 95=\frac{1}{2}at^{2}

190 = a t 2 190=at^{2}

80 = a t 80=at

Solving the system we get t = 2.375 t=2.375

Plugging it back into the equations gives us 80 = a ( 2.375 ) 80=a(2.375)

a = 80 2.375 = 33.68 a=\frac{80}{2.375}=\boxed{33.68}

Parag Motwani
Nov 14, 2013

By third law of motion we know - v²-u²=2 a s.

So the final velocity of the aircraft to be attained is 80m/s. And it starts from rest so initial velocity is zero.The distance to be travelled is 95m.Onapplying this equation we get that the acceleration required must be33.68m/s²

Acceleration is uniform, so, we can use the equation of uniform accelerated bodies, i.e 2 a S = ( v f ) 2 ( v i ) 2 2aS = (v_{f})^{2} - (v_{i})^{2} ,
Where,
a a is the uniform acceleration (which is required in this problem)
v f v_{f} is the final velocity which is attained by the body (in this case the necessary takeoff velocity)
v i v_{i} is the initial velocity of the body (in this case is zero because the jet is initially at rest), and
S S is the distance covered during the motion (in this case is the length of the stream catapult)
rearranging the formula we get:
a = ( v f ) 2 2 S a = \frac{(v_{f})^{2}}{2S}
substituting values in the formula we have:
a = 8 0 2 2 95 a = \frac{80^{2}}{2*95}
Therefore, a = 33.68 a = \boxed{33.68}





Daryab Afridi
Nov 10, 2013

v = 80m/s, s = 95m, a =? using relation: a = v^2 / 2 *S putting the values, we get a = 33.68

v = velocity a = acceleration What is s?

Sorry, Math is my weakness. Next to Math is Physics and Chemistry. Please help me improve.

Jehozaphat Castillo - 7 years, 7 months ago

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s stands for the distance or height.

Apoorva Singh - 7 years, 7 months ago

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and more correctly displacement

Sadman Sakib - 7 years, 7 months ago
Nick Smith
Nov 15, 2013

We know that the distance is equal to the initial velocity times t, plus the integration on acceleration in terms of t which gives the velocity at each point t... We know this distance to be 95 m and the initial velocity to be 0 so...

95 = 1/2a(t^2)

We also know that a = (vf - vi)/t. The final velocity of the jet must be at least 80m/s so a = 80/t

Substituting we get...

95 = 1/2(80/t)(t^2)

190 = 80t^2/t

190 = 80t

t = 2.375

Since a = 80/t

a = 80/2.375 = 33.68m/s^2

Vishnu Agrawal
Nov 12, 2013

use the v^2=u^2+2as (80)^2=u^2+2a95 a=33.68approx=34

Akbarali Surani
Nov 12, 2013

v^2 - u^2 = 2as

v=final velocity = 80 m/s

u=initial velocity = 0 m/s

s=distance=95m

Therefore, a=acceleration=(6400/(2*95))=3200/95

Sazeed Mahmud Sm
Nov 12, 2013

as we know

v 2 v^{2} = u 2 u^{2} + 2 a s

here v=80m/s ; v 2 v^{2} =1600 ( m / s ) 2 (m/s)^{2}

u=0 [time of taking off u of aircraft is fixed ]

s=95m

we get 1600\ ( m / s ) 2 (m/s)^{2} = 2 a 95m

a= 33.68

John Joy
Nov 11, 2013

using the third equation of motion ie is squareof final velocity is equal to intial velocity square plus 2as where a is the accelaration and s is the distance to be covered ...now substitute and find the answer

Diwanshu Tiwari
Nov 11, 2013

Given that-> initial velocity u=0, final velocity=80, distance x=95 using v^{2} = u^{2} + 2ax a= \frac{v^{2} - u^{2}}{2x} on put the values a=33.6842105263158m/s^{2}

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