The correct answers are :
<span>B. The wheels of a bike riding down the street
C. The blades of a fan that is turned on
D. A child sitting on a moving merry-go-round
Let's see why. Keep in mind that the angular momentum is defined as
</span>
<span>where m is the mass of the rotating object, v its velocity and r the radius of the circular trajectory.
</span><span>A. stationary Ferris wheel --> this one has no angular momentum, because its velocity is zero (the wheel is stationary), so v=0 and the angular momentum is zero: L=0
</span>
<span>B. The wheels of a bike riding down the street --> this one has angular momentum, because the edge of the wheel is moving with speed v
</span><span>C. The blades of a fan that is turned on --> this one also has angular momentum, because the fan is moving as well
</span><span>D. A child sitting on a moving merry-go-round --> also this one has angular momentum, which is given by
</span>
<span>where m is the child mass, v its velocity and r the radius of the merry-go-round.</span>
