Answer:
e) 120m/s
Explanation:
When the ball reaches its highest point, its velocity becomes zero, meaning
.
where
is the initial velocity.
Solving for
we get
which is the time it takes the ball to reach the highest point.
Now, after the ball has reached its highest point, it turns around and falls downwards. After time
since it had reached the highest point, the ball has traveled downwards and the velocity
it has gained is
,
and we are told that this is twice the initial velocity
; therefore,

which gives

Thus, the total time taken to reach velocity
is


This
, we are told, is 36 seconds; therefore,

and solving for
we get:



which from the options given is choice e.
Answer:
series
Explanation:
In a series circuit all the components are attached to one branch, so that if one component fails, all the others stop working. In a parallel circuit, however, the components are wired in separate branches, so that even if one branch fails, the rest are not disrupted.
The related concept to solve this exercise is given in the expressions that the magnetic field has both as a function of the number of loops, current and length, as well as inductance and permeability. The first expression could be given as,
The magnetic field H is given as,

Here,
n = Number of turns of the coil
I = Current that flows in the coil
l = Length of the coil
From the above equation, the number of turns of the coil is,

The magnetic field is again given by,

Where the minimum inductance produced by the solenoid coil is B.
We have to obtain n, that

Replacing with our values we have that,



Therefore the number of turn required is 28Truns