A cement block accidentally falls from rest from the ledge of a 53.4-m-high building. When the block is 14.2 m above the ground, a man, 1.91 m tall, looks up and notices that the block is directly above him. How much time, at most, does the man have to get out of the way?
DATA:
Solution:
see the following figure:
First, we calculate the distance the block since released until the man sees it
Now, we calculate the speed of the block when it has fallen 39.2 m:
Replacing values given in data:
Second, we calculate the distance down the block to the man's head:
Now, we calculate the speed of the block when it has fallen a distance :
Replacing values given in data:
Finally, the time (at most) does the man have to get out of the way is calculated using:
Isolating :
Replacing values:
A cement block accidentally falls from rest from the ledge of a 53.4-m-high building. When the...
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