Which sizes influence the adhesive and rolling friction?
1 answer:
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Answer:
E.) conservation of angular momentum
Explanation:
The angular momentum is defined as:
x
where is the radius of the star,
is the mass and
the angular velocity.
and angular momentum is an amount that is conserved, so the angular momentum before the star is compressed must be equal to the angular momentum after the star was compressed:
x
x
the second radius is smaller than the first radius, since the star shrinked, the second angular velocity must be greater that the first.
In other words, the angular velicity increases as the star shrinks because of the conservation of angular momentum.
Given data:
* The extension of the steel wire is 0.3 mm.
* The length of the wire is 4 m.
* The area of cross section of wire is,
* The young modulus of the steel is,
Solution:
The young modulus of the steel in terms of the force and extension is,
where F is the force acting on the steel wire,, l is the original length of the wire, dl is the extension of the wire, and A is the area,
Substituting the known values,
Thus, the force which produce the extension of 0.3 mm of the steel wire is 31.5 N.