<span>An insulator resists conduction of electrons.</span>
Answer:
A) electric field strength between the plates;E = 2 x 10^(6) N/C
B) exit velocity;v = 8.39 x 10^(7) m/s
Explanation:
We are given;
Potential difference; V = 20 kV = 20000 V
Distance between the 2 parallel plates; d = 1cm = 0.01 m
A) The electric field strength will be gotten from;
E = V/d
E = 20000/0.01
E = 2000000
E = 2 x 10^(6) N/C
B) For exit speed, we'll use the formula for Kinetic energy; KE = (1/2)mv²
KE is also expressed as; V•q_e
Thus,
(1/2)mv² = V•q_e
Where;
V is potential difference = 20000 V
Q_e is charge of electron which has a constant value of; (1.6 x 10^(-19))C
m is mass of electron with a constant value of (9.1 x 10^(-31)) kg
v is the velocity
Thus, making v the subject, we have;
v = √((2V•q_e)/m)
v = √((2 x 20000•(1.6 x 10^(-19)))/(9.1 x 10^(-31)))
v = 83862786 m/s or
v = 8.39 x 10^(7) m/s
Going upstream against the current gives a net speed equivalent to the speed at still water minus the speed of the current. Consequently, the speed downstream gives a net speed equal to the speed at still water plus the speed of the current, making it travel faster. The solution is:
UPSTREAM
v = 20 - 1.5 = 18.5 km/h
t = 30 mins or 0.5 hours
distance = 18.5km/h (0.5 h) = 9.25 km
DOWNSTREAM
for the same distance of 9.25 km:
v = 20 + 1.5 = 21.5 km/h
t = 9.25km / 21.5 km/h = 0.43 hours or 25.8 mins = 26 mins --> FINAL ANS.
Answer:
Total moment of inertia when arms are extended: 1.613 
Explanation:
This second part of the problem could be a pretty complex one, but if they expect you to do a simple calculation, which is what I imagine, the idea is just adding another moment of inertia to the first one due to the arms extended laterally and use the moment of inertia for such as depicted in the image I am attaching.
In that image:
L is the length from one end to the other of the extended arms (each 0.75m from the center of the body) which gives 1.5 meters.
m is the mass of both arms. That is: twice 5% of the mass of the person: which mathematically can be written as: 2 * 0.05 * 56.5 = 5.65 kg
Therefore this moment of inertia to be added can be obtained using the formula shown in the image:

Now, one needs to add this to the previous moment that you calculated, resulting in:
0.554 + 1.059 = 1.613 
Answer:
a) 24 J
b) Gravitational Force
c) 45 J
d) 0
e) 6.782m/s
Explanation:
a) m = 3kg
v = 4m/s
h = 1.5m
KE = ?
0.5 * 3 * 16 = 24J
b) Gravitational force
c) F = ma = 3 * 10 = 30N
Work done = Force * distance = 30 * 1.5 = 45J
d) Final Kinetic Energy of the ball is zero because the ball eventually stops moving
e) velocity of ball as it strikes the ground = v
where
v is the velocity as it strikes the ground
u is the initial velocity
a is acceleration
s is the distance
Now since the ball is thrown downwards, a is positive because the velocity of the ball is increasing as the gravitational force acts on it
u = 4m/s
a = 10
s = 1.5
=> 
= 
= 