Answer:
Explanation:
Given
Initial speed 
distance traveled before coming to rest 
using equation of motion

where v=final velocity
u=initial velocity
a=acceleration
s=displacement

for 
using same relation we get

divide 1 and 2 we get


So a distance if 213.32 ft is required to stop the vehicle with 80 mph speed
Answer:

Explanation:
Given:
mass of person, 
mass of merry go-round, 
radius of merry go-round, 
velocity of the person running, 
<u>We consider merry go-round as a ring:</u>
Now the moment of inertial of the ring is given as,



<u>Moment of inertia of the person considering as a point mass:</u>



<u>Now according to the conservation of angular momentum:</u>

where:
angular velocity of the merry-go-round
angular velocity of the person running



Here I =0.4 amp and t=2hr or 2×60×60 sec
We known I=nQ/t where Q is charge and n is no of charge.
n=It/Q
0.4x(2x60x60)/1.6x10^-19