- #1
Darkbound
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Helloo guuuys I've been often reading stuff from this forum and the time for me to get involved has finally came, I am faced with the following problem:
An airliner makes an emergency landing with its nose wheel locked in a position perpendicular to its normal rolling position. The forces acting to stop the airliner arise from friction due to the wheels and from the breaking effort of the engines in reverse thrust mode. The force of the engine on the plane is constant, Fengine = -F0. The sum of the horizontal forces on the airliner can be written as F(t)=-F0+(t/ts-1)*F1, from touchdown at time t=0s to the final stop time at ts=28s the mass of the plane is M=80tonnes, F0=262kN, F1=41kN Neglect all air drag and friction forces, except the one stated in the problem.
a) Find the speed of the plain at touchdown
b) horizontal acceleration at time a(ts) a(0)
c) what distance s does the plane go between touchdown and the final stop time ts
d) What work do the engines during the reverese thrust mode during the landing
e) How much heat energy is absorbed by the wheels during the emergency landing?
Now for a) I am thinking about conservation of momentum, q2-q1= ∫F*dt integrated over the time interval 0->28 which will lead me to the equation v=F*t/m is this correct? I haven't tried inputing the numbers since I have limited submissions and I've noticed that in physics we can often be wrong even that something seems to be right :)
for b) taking the initial velocity which we find in a), is it as simple as (for t=0) a=(v2-v1)/(t2-t1) and since we know that v2 is 0 and t1 is 0 we get a=-v1/t2 and I'm being asked for the absolute value so it turns out a positive number v1/t2 ? What about the acceleration at time = 28s since they are saying that the airlaner stops after 28 seconds shouldn't the acceleration be 0? (i tried 0 its wrong answer)..
for c) well i know the time i know the velocity.. s=v*t?
d) Work = F*s and since the force is negative then I'll get a negative answer for work?
e) Now this is the one that I don't know how to approach, assuming that I am right about all the rest (which I'm pretty sure I'm not :D )
Homework Statement
An airliner makes an emergency landing with its nose wheel locked in a position perpendicular to its normal rolling position. The forces acting to stop the airliner arise from friction due to the wheels and from the breaking effort of the engines in reverse thrust mode. The force of the engine on the plane is constant, Fengine = -F0. The sum of the horizontal forces on the airliner can be written as F(t)=-F0+(t/ts-1)*F1, from touchdown at time t=0s to the final stop time at ts=28s the mass of the plane is M=80tonnes, F0=262kN, F1=41kN Neglect all air drag and friction forces, except the one stated in the problem.
a) Find the speed of the plain at touchdown
b) horizontal acceleration at time a(ts) a(0)
c) what distance s does the plane go between touchdown and the final stop time ts
d) What work do the engines during the reverese thrust mode during the landing
e) How much heat energy is absorbed by the wheels during the emergency landing?
Now for a) I am thinking about conservation of momentum, q2-q1= ∫F*dt integrated over the time interval 0->28 which will lead me to the equation v=F*t/m is this correct? I haven't tried inputing the numbers since I have limited submissions and I've noticed that in physics we can often be wrong even that something seems to be right :)
for b) taking the initial velocity which we find in a), is it as simple as (for t=0) a=(v2-v1)/(t2-t1) and since we know that v2 is 0 and t1 is 0 we get a=-v1/t2 and I'm being asked for the absolute value so it turns out a positive number v1/t2 ? What about the acceleration at time = 28s since they are saying that the airlaner stops after 28 seconds shouldn't the acceleration be 0? (i tried 0 its wrong answer)..
for c) well i know the time i know the velocity.. s=v*t?
d) Work = F*s and since the force is negative then I'll get a negative answer for work?
e) Now this is the one that I don't know how to approach, assuming that I am right about all the rest (which I'm pretty sure I'm not :D )
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