Here we can use the work energy theorem

here we know that

as it come to rest finally



now work done by friction force will be given as


Work done by spring force is given as



so now plug in all data above


so above is the friction coefficient
Force = mass × acceleration
To find acceleration, we can divide the speed by the time it took:
acceleration = 2.40×10^7 / 1.8×10^-9
acceleration = 1.33×10^16
the mass is equal to the mass of an electron
force = (9.11×10^-31)(1.33×10^16)
force = 1.21×10^-14 N
a . true hardness and density are physical properties
Answer:
B'=1.935 T
Explanation:
Given that
magnetic field ,B= 0.645 T
We know that magnetic filed in the solenoid is given as

I=Current
n=Number of turn per unit length
μ0 =magnetic permeability
Now when the current increased by 3 factors
I'=3 I
Then the magnetic filed


B'=3 B
That is why
B' = 3 x 0.645 T
B'=1.935 T
Therefore the new magnetic filed will be 1.935 T.