Work and Power for a Plane Engine

In summary: You can use the KE at each point to find the speed at that point. You can do it all with kinetic energy, but if you want to use potential energy, then don't forget to include the initial speed in the initial kinetic energy.In summary, a 2175 kg test plane with a maximum engine power of 5.28×105 watts accelerates from 46.8 m/s for 6.5 seconds. The initial kinetic energy of the plane is 2.38×10^6 J, and the change in kinetic energy is 3.43x10^6 J. The final kinetic energy of the plane is 5.81x10^6 J. To find the new speed of
  • #1
jojo711
27
0

Homework Statement


A 2175 kg test plane has an engine that can deliver a maximum power of 5.28×105 watts. The pilot hits the throttle when the plane is flying at 46.8 m/s and maintains maximum power for 6.5 seconds.
What is the plane's initial kinetic energy?
What is the plane's change in kinetic energy?
What is the plane's final kinetic energy?
What is the new speed of the plane after the 6.5 seconds?


The Attempt at a Solution


I got the initial kinetic energy to be 1.5 x 10^6 J, but do not know how to get the other parts. Please help!
 
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  • #2
I got a larger answer for the initial KE. Maybe post your work so I can check the details.
The question doesn't mention air resistance, so you must be expected to ignore it. The engine power must be 100% converted to kinetic energy since no efficiency factor is given. So, all you have to do is calculate the amount of work or energy that power amounts to over the 6.5 seconds. Do you have a formula relating power and work?
Add that work energy onto the initial energy, set it equal to Ek = ½mv² and solve for the final v.
 
  • #3
could you please explain more because I really don't understand what you are trying to say but the problems I have to work with:

1/2mv^2
w=fd
p=w/t
 
  • #4
So you have KE = 1/2mv^2 = 1/2*2175*46.8² = ?
I don't get 1.5 x 10^6. Better check it.

Solve your P = W/t formula for W so you can calculate the work done by the engine.
 
  • #5
oh i actually changed it and got

2.38×10^6 J

and then I found the other two answers, and they were both right I got the plane's kenetic energy was 3.43X10^6 J and the final was 5.81x10^6 J.

I still cannot find the last one. What is the new speed of the plane after the 6.5 seconds?
The speed so I have to find velocity? so maybe PE=1/2mv^2?
 
  • #6
Great!
Yes, use so maybe KE=1/2mv^2.
 

FAQ: Work and Power for a Plane Engine

What is the definition of work and power for a plane engine?

Work is defined as the force applied to an object multiplied by the distance that the object moves in the direction of the force. Power is the rate at which work is done, or the amount of work done per unit of time.

How is work and power related to a plane engine?

A plane engine converts the chemical energy of fuel into mechanical work, which is used to power the aircraft. The amount of work done by the engine is directly related to the power it produces.

What factors affect the work and power output of a plane engine?

The work and power output of a plane engine can be affected by factors such as air temperature, air pressure, altitude, engine design, and fuel efficiency. These factors can impact the amount of air and fuel that the engine can take in and convert into work.

How is the work and power output of a plane engine measured?

The work and power output of a plane engine is typically measured in units of horsepower (hp) or kilowatts (kW). This measurement is determined by the amount of work the engine can do in a certain amount of time.

What is the significance of work and power for a plane engine in terms of flight efficiency?

The work and power output of a plane engine directly affect the flight efficiency of the aircraft. A more powerful engine can produce more work and therefore allow the plane to fly faster and more efficiently. Additionally, a more efficient engine can use less fuel, reducing the weight and increasing the overall performance of the aircraft.

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