Answer:
The current of the solenoid is 0.0129 A.
Explanation:
The movement of the electron within the solenoid in a circle is produced by equaling the magnetic force and the centripetal force, as follows:


Where:
I: is the current
m: is the electron's mass = 9.1x10⁺³¹ kg
v: is the electron's speed = 3.0x10⁵ m/s
μ₀: is the permeability magnetic = 4πx10⁻⁷ T.m/A
n: is the number of turns per unit length = 35/cm
r: is the radius of the circle = 3.0 cm
e: is the electron's charge = 1.6x10⁻¹⁹ C
Therefore, the current of the solenoid is 0.0129 A.
I hope it helps you!
Answer:
B. +5.75 m/s
Explanation:
When there are two bodies, a and b, whose velocities measured by a third observer (in this case, the ground) are
and
respectively, the relative velocity of B with respect to A is given by:

Thus, the velocity of the girl relative to the lawnmower is:

let the distance of pillar is "r" from one end of the slab
So here net torque must be balance with respect to pillar to be in balanced state
So here we will have

here we know that
mg = 19600 N
Mg = 400,000 N
L = 20 m
from above equation we have



so pillar is at distance 10.098 m from one end of the slab
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