Answer:
A) Must be done 19806.62 joules of work.
B) The average power is 1320.44 Watts.
Explanation:
A) First, we're going to use the work-energy theorem that states total work (
) done on an object is equal to the change in its kinetic energy (
):
(1)
So, all we must do is to find the change on kinetic energy. Because we're working with rotational body, we should use the equation 
for the kinetic energy so:
(2)
with 
the initial angular velocity, 
the final angular velocity (is zero because the wheel stops) and I the moment of inertia that for a thin hoop is 
, using those on (2)
(3)
By (3) on (1):
B) Average power is work done divided by the time interval:
NOTE: We use the relation 
to convert 280 rev/min(rpm) to 29.32 rad/s
1) When you look toward the Galactic Center with your eye, you see a long, thin strip. This suggests a disk seen edge-on, rather than a ellipsoid or another shape. We can also detect the bulge at the center. Since we see spiral galaxies which are disks with central bulges, this is a bit of a top.
Answer:
When you are running the most important force that you should understand is friction. Friction is a force that opposes movement between two objects, but for runners friction makes you faster. Friction gives you a better and more efficient way to use your energy into speed.
