A magnetic field is a force field, invisibly pushing electrically charged objects just as a gravitational field pulls objects with mass. Whereas all objects with mass exert a gravitational field, however, not all objects have a magnetic field. Magnetic fields are created by electrical charges. Thanks to their structure at the atomic level, some substances -- like the iron in magnets -- have a permanent magnetic field.
Answer:
The time taken by the student to climb is 12.25 seconds and work done is 2450 J.
Explanation:
Given that,
Mass of the student, m = 50 kg
The student climbs to a height of 5 meters at a constant speed.
The student's power output is 200.0 W, P = 200 W
The power of an object is given by work done divided by time taken. So,

(b) W is work done,

(b)

So, the time taken by the student to climb is 12.25 seconds and work done is 2450 J.
Answer:
The correct answer is -
A) 
B) 
Explanation:
As it is mention that the spool has mass M, radius R and moment of inertia I. In the first part of the question as the spool is not moving and r < R which means there is net torque = 0
so, 
and 
In the second part of the question from the given information, we can express the angular acceleration
=
( alpha = angular acceleration and a = translational acceleration)
The resistance of a wire is given by

where

is the resistivity of the material, L the length of the wire and A its cross-sectional area.
In the problem,

and L remain the same, while A changes because the radius changes. The area is given by:

This means that if we double the radius (2r), the area becomes

And therefore, the new value of the resistance is

So, when the radius is doubled, the resistance becomes

of its original value.
9 ounces bc if he does then he wont be so like ugh I'm out of wonder land yeah 9 ounces deffo