+3 votes
in JEE by kratos

A jetliner, travelling northward, is landing with a speed of 69 m/. Once the jet touches down, it has 750 m of runway in which to reduce its speed to 6.1 m/ . Compute the average acceleration (magnitude and direction) of the plane during landing.

1 Answer

+3 votes
by kratos
 
Best answer

We organize ourselves by drawing a picture of the landing plane, as shown in Fig. The plane touches down at x = 0; that’ where the motion begins, as far as we’re concerned. The initial velocity is v0 = 69 m/ . In the final position (after it has travelled the full extent of the runway), x = 750 m and v = 6.1 m/* . But we are not given the time t for this motion to take placed and we don’t know the (constant) acceleration a.

If we want to get a we can use the below eqn. because it doesn’t contain the time t. Plugging in the numbers, we get

We get a negative answer, and we expect that; the plane’* velocity (in the direction of motion, North) is decreasing. The acceleration has a magnitude of 3.15 m/s2 and its direction is opposite the direction of motion, i.e. South.

...