Question

An airbys A380 airliner lands at 30 m/s. Partially loaded, its mass is 480000 kg. The engines apply reverse thrust for 12s to slow the plane to 25 m/s.How much thrust did the engines apply?

Answer 1

To determine the thrust applied by the engines, we can use Newton's second law of motion, which states that force (thrust) is equal to mass times acceleration. In this case, we need to calculate the force required to decelerate the plane from 30 m/s to 25 m/s in 12 seconds.

First, we calculate the change in velocity (∆v):

`\displaystyle\sf \Delta v=25\,m/s-30\,m/s=-5\,m/s`

Next, we calculate the acceleration (∆a) using the formula:

`\displaystyle\sf \Delta a=(\Delta v)/(\Delta t)`

where ∆t is the change in time, which is 12 seconds in this case.

`\displaystyle\sf \Delta a=(-5\,m/s)/(12\,s)`

Now, we can determine the force (thrust) applied by the engines using Newton's second law:

`\displaystyle\sf F=m\cdot a`

where m is the mass of the airplane, which is 480000 kg.

`\displaystyle\sf F=480000\,kg\cdot \left((-5\,m/s)/(12\,s)\right)`

Calculating the result:

`\displaystyle\sf F=-200000\,N`

Therefore, the engines applied a thrust of -200000 Newtons (N) to decelerate the plane. The negative sign indicates that the thrust is in the opposite direction of the motion.