What fraction of the engine power is being used for the place to fly

AI Thread Summary
The discussion revolves around calculating the fraction of engine power used by a small single-engine airplane to climb. Initially, the user attempted to calculate this using only the climbing velocity, resulting in an incorrect figure of 2.4%. After realizing the need to account for gravitational force, the correct formula incorporates both the climbing speed and gravitational acceleration. The final calculation yields that approximately 23.8% of the engine's 76 kW power is utilized for climbing. The conversation highlights the importance of including gravitational effects in power calculations for accurate results.
cantgetno
Messages
23
Reaction score
0

Homework Statement


When its engine of power 76 kW is generating full power, a small single-engine airplane with mass 660 kg gains altitude at a rate of 2.8 m/s.
What fraction of the engine power is being used to make the airplane climb?

Homework Equations


total power=76x10^3 W
mass=660 kg
dx/dt=velocity=2.8 m/s

Power=mass x velocity

The Attempt at a Solution


(660x2.8)/(76x10^3) x 100 = 2.4% but this is wrong and I am not sure where I've gone wrong
 
Physics news on Phys.org


cantgetno said:

Homework Statement


When its engine of power 76 kW is generating full power, a small single-engine airplane with mass 660 kg gains altitude at a rate of 2.8 m/s.
What fraction of the engine power is being used to make the airplane climb?

Homework Equations


total power=76x10^3 W
mass=660 kg
dx/dt=velocity=2.8 m/s

Power=mass x velocity

The Attempt at a Solution


(660x2.8)/(76x10^3) x 100 = 2.4% but this is wrong and I am not sure where I've gone wrong

There's no gravity?
 


oh of course

660(2.8+9.8)/(76x10^3) x 100 =10.9%

is that it?
 


cantgetno said:
oh of course

660(2.8+9.8)/(76x10^3) x 100 =10.9%

is that it?

No. Because Power is Work / time = Force * distance / time

In this case it is P = m*g *v
 


OK i get what you mean

so its:

660x2.8x9.8 / 76x10^3 x 100 = 23.8

thank you lots
 


cantgetno said:
OK i get what you mean

so its:

660x2.8x9.8 / 76x10^3 x 100 = 23.8

thank you lots

There you go.

Cheers.
 
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Thread 'Variable mass system : water sprayed into a moving container'
Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
Back
Top