As shown in the figure, point A is the perpendicular of MN, and point B is the vertical foot.

then what AB=AP×sin30 = 160×0.5=80m

∵? AB=80m< 100m

∴? Schools will be affected by noise.

Make a circle with point A as the center and 100m as the radius, and intersect MN at points C and D. ..

Then, when the tractor runs along the PN direction on the MN highway, its noise will have an impact on the schools in the area of the CD section.

CD=2√( 100？ -80? )= 120m

Tractor speed =18km/h = 5m/s.

How long does it take the tractor to pass the CD section? t= 120/5=24s

That is, when the tractor is driving along the MN highway, its noise has a 24-second impact on the school.