Question

An airplane flies at 100km/h in still air. If it flies into a 10 km/h headwind, its groundspeed is

A) 100 km/h
B) 110 km/h
C) 120 km/h
D) 90 KM/h

Answer 1

its D.) 100-10 is 90 the plane is flying in the 10 km/h wind at 100 km/h take away the resistance and you get your ground speed

Answer 2

D)
`90(km)/(h)`

Step-by-step explanation:

The groundspeed of the airplane is equal to the speed of the airplane in still air, plus the speed of the air. Since the plane flies with headwind, the sign of the air speed is negative, since it is contrary to the movement of the airplane.

Now, we have:

`V_g=V_a+V_h`

Here
`V_g` is the airplane groundspeed,
`V_a` the airplane speed and
`V_h` the air speed

`V_g=100(km)/(h)+(-10(km)/(h))=90(km)/(h)`