A stone from the edge of the balcony of a building makes a free fall motion to the ground and carrie

B's displacement in the first period of time is 2m, so <>

Free fall is a linear motion with uniform variable speed, so it is <>

Therefore<> the displacement in the second period is 6m, and the displacement in the third period is 10m, so the height of the balcony is correct.

According to the fact that the free fall motion is a uniformly accelerated linear motion with an initial velocity of 0, the ratio of displacements in equal time intervals from rest is: 1:3:5 to get:

Its displacement in the third period is: s3 =5 s1 =5 so choose C

Question C Analysis: If an object moving in a straight line with a uniform acceleration with an initial velocity of zero, the ratio of the displacement in the same time from the beginning of rest is <>

This shows the <>

That is<> so <>

Therefore, choose C Comment: To solve this problem, it is necessary to know that the ratio of the displacement in the equal time interval from the beginning of the rest is <> for the uniform acceleration linear motion with an initial velocity of 0

Let the first period of motion be t, then.

The displacement within ts is: h1

gtt=2hgs=

The total time of the free fall motion is three times the time of the first period of motion, so the total time of 3s is based on h=1

gt de. h=1m=18m, so the balcony height is 18m

So choose B

Let the first motion time be t, then the displacement in ts is: h1gt solution: t=

The total time of the free fall motion is three times the time of the first period of motion, so the total time of 3s is based on h=1

gt: h=1

m=18m, so the balcony height is 18m

So choose B