How Much Work Does a Plane's Engine Perform to Reach 3200m at 65m/s?

AI Thread Summary
The discussion revolves around calculating the minimum work done by a plane's engine to ascend to 3200 meters while reaching a speed of 65 m/s. The plane's mass is 1500 kg, and the problem emphasizes the use of conservation of energy rather than kinematic equations. The key takeaway is that the change in kinetic energy and potential energy must be considered to find the total work done, which is calculated to be 5.0 x 10^7 joules. Participants clarify that potential energy is zero at ground level, and the energy is converted during ascent. The conversation highlights the importance of understanding energy conservation in solving such physics problems.
Some_Thing
Messages
5
Reaction score
0

Homework Statement



A 1500 kg plane, initially at rest, leaves an airfield and a short time later it is at an elevation of 3200 m traveling at 65 m/s. What is the minimum work done by the plane's engine in this time? (Ignore air resistance)


Homework Equations



W=Fd, F=ma, and most certainly some other ones.


The Attempt at a Solution



This is what I understand from the question:

Vox = 0 m/s

Voy = 0 m/s

dy = 3200 m

m = 1500 kg

I assume that at 3200m, the plane starts to fly only horizontally, so "65 m/s" would be Vfx.


The problem is that this seems insufficient for any of the kinematics formulas, and I don't see how I could use it in different areas (like dynamics).


What am I missing here? Can someone please give me a push in the right direction?

Any help is greatly appreciated,

Thanks.
 
Physics news on Phys.org
Kinematic equations won't do you any good here. Can you tell me which quantity is conserved in this system?
 
Cyosis said:
Kinematic equations won't do you any good here. Can you tell me which quantity is conserved in this system?

Ah, I see, its one of those conservation of energy questions, isn't it?

Change in Ek + Change in Ep = the correct answer (5.0 x 10^7)

Thanks!


One thing bugs me though. Shouldn't these two add up to 0?
 
Some_Thing said:
Ah, I see, its one of those conservation of energy questions, isn't it?

Change in Ek + Change in Ep = the correct answer (5.0 x 10^7)

Thanks!


One thing bugs me though. Shouldn't these two add up to 0?

Why would they add up to zero?

There is no potential energy on the ground. The change in kinetic energy on the ground is converted to potential energy at 3200m in the air and kinetic energy to make it travel at 65m/s
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
Thread 'Voltmeter readings for this circuit with switches'
TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
Back
Top