A Boeing 747 ""Jumbo Jet"" has a length of 59.7 m. The runway on which the plane lands intersects another runway. The width of the intersection is 25.0 m. The plane decelerates through the intersection at a rate of 5.70 m/s2 and clears it with a fi nal speed of 45.0 m/s. How much time is needed for the plane to clear the intersection?

1.7 seconds

Explanation:

To clear the intersection, the total distance to be covered = 59.7 + 25 =84.7m

first we need to find the initial speed to just enter the intersection by using the third equation of motion

v^2 - u^2 = 2*a*s

45^2 - u^2 = 2 * -5.7 * 84.7

u^2 = 45^2 +965.58

u^2 = 2990.58

u = 54.7 m/s

Now for time we apply the first equation of motion

v-u =a * t

t = (v-u)/a = (45 - 54.7)/-5.7 = 1.7seconds

pe = weightxheight = 2000x1000=2,000,000joules

i think the answer is a, hope this : )