Answer:
Frictional force always acts parallel to two planes in contact with each other and in a direction opposite to that of relative motion of the two bodies. 2. Frictional forces are caused due to intermolecular interactions between the bodies. Frictional force is more for rough surface and less for smooth surfaces.
Inertness, especially with regard to effort, motion, action, and the like; inactivity; sluggishness.
-- Gravity makes a falling object fall 9.8 m/s faster every second.
-- So, it reaches the speed of 30 m/s in (30/9.8) = 3.06 seconds after it's dropped.
-- The distance an object falls from rest is D = 1/2 (acceleration) (time)²
D = 1/2 (9.8 m/s²) (3.06 sec)²
D = (4.9 m/s²) (9.37 sec²)
<em>D = 45.8 meters</em>
Notice that we don't care how high the building is. The problem works just as long as the object can reach 30 m/s before it hits the ground. That turns out to be anything higher than 45.8 meters for the drop . . . maybe something like 13 floors or more.
Now I'll go a little farther for you ! Writing the last paragraph made me a little curious and uncomfortable. So I went and looked up the world's tallest buildings . . . and I found out that this problem could never happen !
The tallest building in the world now is the Burj Khalifa, in Dubai. It has 163 floors, and it's 828 meters high ! That's 2,717 feet. It's gonna be a long time before there's a building that's 1125 meters tall, like this problem says. That's close to 3700 feet . . . I've had flying lessons where I wasn't that far off the ground !
