![](../../image/prcpywrt.gif)
An airplane rolls down a runway with its engines at full throttle. The engines
generate a forward thrust of 30,000N. There is also a drag force of 10,000N due to air friction.
The total force on this airplane is
(A) 40,000N forward.
(B) 30,000N forward.
(C) 20,000N forward.
(D) 10,000N backward
(E) 10,000N upward
![](../../image/prcpywrt.gif)
An airplane rolls down a runway with its engines at full throttle. The engines
generate a forward thrust of 30,000N. There is also a drag force of 10,000N due to air friction.
The total force on this airplane is
(A) 40,000N forward. --- No.
Thrust and drag components have opposite signs.
![](../../image/prcpywrt.gif)
An airplane rolls down a runway with its engines at full throttle. The engines
generate a forward thrust of 30,000N. There is also a drag force of 10,000N due to air friction.
The total force on this airplane is
(B) 30,000N forward. --- No.
Add both force components.
![](../../image/prcpywrt.gif)
An airplane rolls down a runway with its engines at full throttle. The engines
generate a forward thrust of 30,000N. There is also a drag force of 10,000N due to air friction.
The total force on this airplane is
(C) 20,000N forward. --- Yes.
30,000N - 10,000N.
![](../../image/prcpywrt.gif)
An airplane rolls down a runway with its engines at full throttle. The engines
generate a forward thrust of 30,000N. There is also a drag force of 10,000N due to air friction.
The total force on this airplane is
(D) 10,000N backward --- No.
Add both force components.
![](../../image/prcpywrt.gif)
An airplane rolls down a runway with its engines at full throttle. The engines
generate a forward thrust of 30,000N. There is also a drag force of 10,000N due to air friction.
The total force on this airplane is
(E) 10,000N upward --- No.
The airplane is rolling, so it is in vertical equilibrium.