I think it may be c, 1.7 v. I work with electricity a lot.
Answer:
The tension in the rope is 20 N
Solution:
As per the question:
Mass of the object, M = 2 kg
Density of water, 
Density of the object, 
Acceleration due to gravity, g = 
Now,
From the fig.1:
'N' represents the Bouyant force and T represents tension in the rope.
Suppose, the volume of the block be V:
V =
(1)
Also, we know that Bouyant force is given by:

Using eqn (1):


From the fig.1:
N = Mg + T
40 = 2(10) + T
T = 40 - 20 = 20 N

Answer:
Those substances which can conduct electricity are called conductors, while those substances which don't conduct electricity are called insulators.
Resistance is the obstruction provided by the material through which the current passes,so since conductors conduct electricity and insulators don't,so the obstruction i.e resistance provided by the conductor must be less,while insulators being unable to conduct electricity,has very high resistance.
Example of conductor is copper
Example of insulator is plastic
To solve this problem we must basically resort to the kinematic equations of movement. For which speed is defined as the distance traveled in a given time. Mathematically this can be expressed as

Where
d = Distance
t = time
For which clearing the time we will have the expression

Since we have two 'fluids' in which the sound travels at different speeds we will have that for the rock the time elapsed to feel the explosion will be:


In the case of the atmosphere -composite of air- the average speed of sound is 343m / s, therefore it will take


The total difference between the two times would be


Therefore 3.357s will pass between when they feel the explosion and when they hear it