A jet plane starts from rest on the runway and accelerates for takeoff at 2.30 m/s² (= 7.55 ft/s²). It has two jet engines, each of which exerts a thrust of 1.40 × 10⁵ N ( = 15.7 tons). What is the weight of the plane?

We will determine the weight of the plane step by step.

Step 1: Understanding Given Data
Initial velocity, u = 0 (since the plane starts from rest)
Acceleration, a = 2.30 m/s²
Thrust of each engine = 1.40 × 10⁵ N
Total thrust from both engines = 2 × (1.40 × 10⁵ N) = 2.80 × 10⁵ N
Weight of the plane (W) = ?
Step 2: Finding the Mass of the Plane
From Newton’s Second Law:

Force (F) = Mass (m) × Acceleration (a)

Here, the total force applied is the total thrust:

2.80 × 10⁵ N = m × 2.30 m/s²

Solving for m:

m = (2.80 × 10⁵) / 2.30
m = 1.217 × 10⁵ kg

Step 3: Calculating Weight of the Plane
Weight (W) is given by:

W = m × g, where g = 9.81 m/s² (acceleration due to gravity)

W = (1.217 × 10⁵) × 9.81
W = 1.19 × 10⁶ N

Final Answer:
The weight of the plane is 1.19 × 10⁶ N.