Final answer:
To stay beneath the airplane traveling at 120 km/h at a 49° angle, the truck must match the horizontal component of the airplane's velocity, which can be found using the formula Vh = V * cos(θ).
Step-by-step explanation:
To determine how fast the truck must travel to stay beneath the airplane, we need to calculate the horizontal component of the airplane's velocity. The airplane is moving at a speed of 120 km/h at an angle of 49° to the ground. Using trigonometry, we can find the horizontal component of the airplane's velocity which is what the truck needs to match to stay beneath the airplane.
The horizontal velocity Vh of the airplane can be calculated using the cosine function:
Vh = V * cos(θ)
where:
V is the speed of the airplane (120 km/h), and
θ is the angle of the airplane's direction with respect to the ground (49°).
Now plug in the values to get:
Vh = 120 km/h * cos(49°)
Calculating this gives us the truck's required velocity to stay beneath the airplane.