There are two different ways to understand time and these are:
A. What time is it?
B. How much time?
The examples of these two different ways are:
A. What time is it? The best example that would help us understand and know what time are the clock and the calendar. This gives us the exact hour, minutes and seconds. The calendar tells us the exact day, month and year.
B. How much time? This makes us understand how much time did it take from the starting time. An example for this would be a stopwatch.
Answer:
59.4 meters
Explanation:
The correct question statement is :
A floor polisher has a rotating disk that has a 15-cm radius. The disk rotates at a constant angular velocity of 1.4 rev/s and is covered with a soft material that does the polishing. An operator holds the polisher in one place for 4.5 s, in order to buff an especially scuff ed area of the floor. How far (in meters) does a spot on the outer edge of the disk move during this time?
Solution:
We know for a circle of radius r and θ angle by an arc of length S at the center,
S=rθ
This gives
θ=S/r
also we know angular velocity
ω=θ/t where t is time
or
θ=ωt
and we know
1 revolution =2π radians
From this we have
angular velocity ω = 1.4 revolutions per sec = 1.4×2π radians /sec = 1.4×3.14×2×= 8.8 radians / sec
Putting values of ω and time t in
θ=ωt
we have
θ= 8.8 rad / sec × 4.5 sec
θ= 396 radians
We are given radius r = 15 cm = 15 ×0.01 m=0.15 m (because 1 m= 100 cm and hence, 1 cm = 0.01 m)
put this value of θ and r in
S=rθ
we have
S= 396 radians ×0.15 m=59.4 m
The ozone layer absorbs UV
(ultraviolet) radiation. The answer is letter C. the ozone layer is able to
oxidize the electros and photons in the UV rays so that the light that can pass
through can be not harmful to humans.
