Incomplete question.The Complete question is here
A flat uniform circular disk (radius = 2.00 m, mass = 1.00 ✕ 102 kg) is initially stationary. The disk is free to rotate in the horizontal plane about a friction less axis perpendicular to the center of the disk. A 40.0-kg person, standing 1.25 m from the axis, begins to run on the disk in a circular path and has a tangential speed of 2.00 m/s relative to the ground.
a.) Find the resulting angular speed of the disk (in rad/s) and describe the direction of the rotation.
b.) Determine the time it takes for a spot marking the starting point to pass again beneath the runner's feet.
Answer:
(a)ω = 1 rad/s
(b)t = 2.41 s
Explanation:
(a) initial angular momentum = final angular momentum
0 = L for disk + L............... for runner
0 = Iω² - mv²r ...................they're opposite in direction
0 = (MR²/2)(ω²) - mv²r
................where is ω is angular speed which is required in part (a) of question
0 = [(1.00×10²kg)(2.00 m)² / 2](ω²) - (40.0 kg)(2.00 m/s)²(1.25 m)
0=200ω²-200
200=200ω²
ω = 1 rad/s
b.)
lets assume the "starting point" is a point marked on the disk.
The person's angular speed is
v/r = (2.00 m/s) / (1.25 m) = 1.6 rad/s
As the person and the disk are moving in opposite directions, the person will run part of a revolution and the turning disk would complete the whole revolution.
(angle) + (angle disk turns) = 2π
(1.6 rad/s)(t) + ωt = 2π
t[1.6 rad/s + 1 rad/s] = 2π
t = 2.41 s
Explanation:
everything can be found in the picture
This is what wiki says hope it helps
A displacement is a vector whose length is the shortest distance from the initial to the final position of a point P.[1] It quantifies both the distance and direction of an imaginary motion along a straight line from the initial position to the final position of the point.
A displacement may be also described as a 'relative position': the final position of a point (Sf) relative to its initial position (Si), and a displacement vector can be mathematically defined as the difference between the final and initial position vectors:
<u>Question:</u>
You are working on an experiment involving a very strong permanent magnet, and your data suggests that your magnet's field suddenly decreased during some interval in time. Such a decrease could have been caused by the magnet
A. Having overheated substantially
B. Being hit hard
C. Both A and B
D. Being grounded out
<h3><u>Answer:</u></h3>
A decrease in magnetic field of the permanent magnet have been caused by the magnet having overheated substantially or sharp impacts by being hit hard.
Option c
<h3><u>Explanation: </u></h3>
Permanent magnets are ferromagnetic materials with its magnetic domains aligned and grouped together in the same direction. These atomic domains maintain their directionality and hence a permanent magnet provides persistently strong magnetic fields without quick weakening. Some factors may lead to demagnetization or else a consistent reduction in magnetic strength.
Overheating a magnetic material realigns the magnetic domain regions and affects its directionality. When it reaches to a temperature defined as Curie temperature, varying with each material; the substance is no more a magnet due to complete randomness in the domain structure. As the temperature decreases and approaches the room temperature, magnetic field appears but is less in strength. Sudden impacts due to hitting may lead to random realignment of magnetic domains and thus decrease its magnetic strength.
